Is fasting good for diabetics?

Through a series of books and YouTube videos, Dr. Fung has attracted loyal followers who are convinced he has the answer to their diabetes problems.

Dr. Fung says he decided to experiment with intermittent fasting because he was frustrated seeing so many diabetic patients with kidney failure. “It occurred to me that fasting was an underutilized therapeutic option for losing weight,” he recalls. “I started doing this five years ago, and a lot of people got incredibly good results – it reversed their diabetes.”

Type 2 is the most common form of diabetes accounting for 85 to 90 per cent of cases. It usually develops later in life and it’s often associated with being overweight.

A major feature of the disease is a condition known as insulin resistance. Insulin is a hormone that moves glucose (sugar), from the bloodstream into the body’s cells where it is used for energy. For a variety of reasons that are not fully understood, the body’s tissues don’t respond adequately to insulin and glucose then becomes elevated in the bloodstream.

Poorly controlled blood-sugar levels can lead to a host of medical complications, increasing the risk of heart attack, stroke, kidney failure, blindness and limb amputation.

Diabetes is often treated with medications to make the body more responsive to insulin. Some patients also take additional insulin to top up the amount produced by their own bodies.

Dr. Fung believes the medical community “has been treating type 2 diabetes incorrectly.” In particular, he argues, that the medications used to clear sugar from the bloodstream end up overstuffing cells with glucose, which gets turned into fat. “Even if your blood-sugar gets better, you gain weight and your diabetes is only getting worse.”

According to Dr. Fung, cells are insulin resistant because they are already filled to the maximum with glucose. He compares insulin resistance to a suitcase that’s packed full of clothes. You can’t get more clothes in without taking some out, he explains.

“Periods of fasting allow the body to burn off the excess sugar and then the cells become responsive to the insulin once again.”

He also encourages patients to modify their diets, by cutting back on refined carbohydrates – such as bread and pasta made from white flour – which the body quickly converts into glucose and by adding healthy fats found in avocadoes, nuts and olive oil.

Once glucose stores are depleted, which happens after prolonged fasting, the body shifts to burning fat for fuel.

By fasting regularly, he says, patients tend to lose weight, their insulin resistance is overcome, and they can cut back or even stop taking their diabetes medications.

“Type 2 Diabetes is an entirely reversible disease,” he insists, challenging the traditional notion that’s a chronic and often progressive condition.

Despite his unconventional views, Dr. Fung is winning some converts in the medical profession. “It’s not for everybody, but if someone is motivated, it sure makes sense as a way to lose weight,” says Dr. Martin Strauss, a cardiologist at North York General Hospital.

Over the past two years, Dr. Strauss, who is also an assistant professor at the University of Toronto, says he has referred about 50 patients to Dr. Fung for treatment. “I would say 30 to 40 per cent of them stick with it.”

Dr. Fung agrees that not everyone will succeed at intermittent fasting. He also notes that patients need medical supervision – especially if they are taking diabetes medications. The doses of their drugs will likely need to be adjusted over time.

He says patients with diabetes should at least give it a try. “If you don’t like it, or you feel unwell, you can stop immediately.”

But most doctors are unlikely to recommend intermittent fasting without more scientific evidence that it can produce lasting results.

“We need a proper study with enough patients for a long duration of time to really prove whether this is safe and effective – or harmful,” says Dr. Jeremy Gilbert, an endocrinologist at Sunnybrook Health Sciences Centre in Toronto.

“All diets work in the short-term, but it’s the maintenance phase that’s so difficult,” he says.

There is a risk that those who attempt it and fail could end up worse off, speculates Annie Hoang, a registered dietitian at Sunnybrook. An individual’s metabolism might switch into “starvation mode,” reducing the amount of energy needed at rest, she explains. That means some patients could regain all the weight they lost – and more – if they stop doing intermittent fasting.

Dr. Fung argues that won’t happen.

Whatever the case, Dr. Gilbert says, “this diet has some extreme components some of which makes sense, but it’s not clear how many people can actually do what he (Dr. Fung) is recommending indefinitely.”

Dr. Fung says he has personally treated more than a thousand patients over the past five years “with many of them sustaining their non-diabetic status over the duration.”

But he has not yet published in a peer-reviewed journal the data showing his patients’ actual rate of success.

“Intermittent fasting is not something I would necessarily recommend until we know more,” says Dr. Nicola Guess, a lecturer and nutrition researcher at King’s College London.


Is Intermittent Fasting Safe for People With Diabetes?

When the now 46-year-old Mary Roberts from Lockhart, Texas, was diagnosed with type 2 diabetes in 2008, her doctor immediately put her on Metformin (glucophage), a drug to help stabilize blood sugar. “When I got the diagnosis, I guess I wasn’t surprised,” says Roberts, explaining that not only was she overweight but her mom had been on insulin for type 2 diabetes.

Not wanting to be on medication herself for her entire life, Roberts set out on a path to control the diabetes through diet, but a few years of nutrition classes proved unsuccessful in lowering her blood sugar level. It was after her doctor suggested insulin on top of the high dose of Metformin that Roberts switched gears. “I really wanted to find a way to get healthy,” she says.

She found the solution in changing her approach to eating — just not the way she expected. Intermittent fasting (IF) combined with the popular ketogenic diet, which emphasizes dramatically reducing carbohydrate intake, helped her lose weight and lower her A1C. “I feel amazing,” Roberts says.

What Is Intermittent Fasting and How Is It Done?

Although IF has become more popular in recent years, the diet plan isn’t new. In fact, many religions (including Christianity, Judaism, and Islam) have followers who practice fasting of some variety throughout the year. Fasting is often required for blood tests, medical procedures, or surgery. The reason IF has gained so much attention recently is likely due to the release of new diet books plugging the plans and celebrity endorsements. “I think that it has gained popularity because anytime a person drastically cuts calories from their diet, they’re going to lose weight. And we’re so results driven that by seeing that happen we think, This is a great solution,” says Despina Hyde Gandhi, RD, CDE, a dietitian at NYU Langone’s Weight Management Program and the president of the Greater New York Dietetic Association.

There are different ways to do IF, including skipping meals and eating only during a certain time period, as well as restricting calories on certain days of the week and eating normally on other days.

Roberts decided to fast by eating two meals a day, but she never follows a strict schedule. “I eat when I’m hungry,” she says.

Within a few months, Roberts’ blood glucose level went from over 200 milligrams per deciliter (mg/dL) to around 130 mg/dL, and within eight months, it was within a normal range. Her blood glucose level now is always in the 80s and 90s, and her A1C, a two- to three-month average reading of blood sugar, is 4.8, which is also normal. After 22 months, she lost 106 pounds and has since kept it off. “Sometimes I pinch myself I can’t believe I did this. I turned it around,” she says.

The Potential Benefits of Intermittent Fasting for Diabetes

In previous years, dietitians and scientists thought of IF as a negative practice, so there isn’t a wealth of high-quality clinical research on how it may affect people with diabetes, says Jason Fung, MD, a nephrologist in Toronto and the co-author of The Complete Guide to Fasting: Heal Your Body Through Intermittent, Alternate-Day, and Extended Fasting. But attitudes have begun to change, and some preliminary studies suggest the approach may have benefits, including for people with diabetes.

For example, an early study published in August 2017 in the journal Autophagy found that IF helped preserve beta cells in mice that were manipulated to have obesity-induced diabetes. The combination of beta cell loss and insulin resistance lead to the high blood sugar that marks type 2 diabetes, according to an article published in March 2013 in Frontiers in Endocrinology.

That study was only done in rodents, which doesn’t necessarily mean the same benefits would be seen in humans — nor does it prove that the diet would be safe for people with diabetes. But other research offers clues: One very small observational study, published in April 2017 in the World Journal of Diabetes, suggests short-term daily IF may help improve fasting glucose, weight, and the postmeal blood sugar level in people with type 2 diabetes. Although the study involved just 10 participants, and it was not a randomized controlled trial — the golden standard for research — the findings may hold truth based on what we already know about weight loss. “There’s no denying that anytime you cut calories from your diet, you’re going to see the scale drop,” Gandhi says. That potential aspect of IF can lead to improvements in insulin sensitivity, too, says Michael Mosley, MD, a science journalist and the author of The FastDiet. Further research needs to be conducted to see if IF is truly safe for the larger group of people with type 2 diabetes.

While research on IF for diabetes prevention is also in its early stages, one study published in May 2011 in the International Journal of Obesity found that women who followed an IF diet two days per week and those who followed a more traditional consistent calorie reduction seven days per week lost weight. Those in the two-day group saw the greatest weight loss, yet they had only a modest reduction in fasting insulin, a measure of the insulin level over time, and insulin resistance.

Why Intermittent Fasting May Harm Blood Sugar Control

Nevertheless, experts say that IF carries risks, especially when you have diabetes and need to keep blood sugar stable.

For starters, skipping whole meals can actually result in poorer blood glucose control, not to mention issues like fatigue, low energy during workouts (and thus an increased risk of injury), and medication imbalances. It may also lead to worse diet choices, having the opposite impact on your waistline and blood sugar. People who restrict calories may be more inclined to reach for carb-heavy fare, for instance. “Then their blood sugar is going to go very high and going to be erratic throughout the day,” Gandhi says.

Plus, severely restricting calories or skipping meals can be a hard plan to stick with. “The problem with fasting is it may be more difficult to maintain in the long term,” says Ruth S. Pupo, RDN, CDE, who practices at White Memorial Medical Center in Los Angeles. While losing weight can be beneficial for people with diabetes, as it increases insulin sensitivity, putting weight back on can have the opposite effect, thereby increasing the risk for diabetes complications.

Furthermore, certain people, like pregnant and breast-feeding moms, should avoid IF, as should those with an underlying disease or medical condition, Pupo says. “Anytime you have a higher demand for more nutrition, you don’t want to do a fast,” she says, explaining that both pregnant and breast-feeding moms require extra calories for themselves and their babies, and fasting can cause them to run out of glucose and burn fat, tissue, and muscle. What’s more, if a pregnant mom overproduces ketones (substances that are produced when the body uses fat for fuel), the effect can be harmful to the fetus.

Likewise, for someone with an overactive thyroid, IF can lead to what’s called a “thyroid storm,” which causes an increase in temperature, a rapid heart rate, and possibly even cardiac arrest because of the added stress, Pupo says.

Another risk of IF for people with diabetes is hypoglycemia, or low blood sugar. According to a study published in September 2016 in the journal BMJ Global Health, of 150 people with diabetes who fasted regularly, 10 percent experienced hypoglycemia. People who are on certain diabetes medications, like sulfonylureas and insulin in particular, may be at an increased risk of this complication, which can be life-threatening.

Most important, because of the dangers of blood sugar fluctuation that IF may cause, Gandhi personally advises against the diet plan for people with type 2 diabetes. “It’s not great for diabetes because we don’t want to have those dips, those highs and lows in blood sugar. The goal with diabetes is to maintain a steady and stable blood sugar throughout the day,” Gandhi says.

People with diabetes also run the risk of diabetic ketoacidosis, which is a complication of diabetes that occurs when the body can’t produce enough insulin. Insulin brings glucose into the cells, but when the body doesn’t have enough insulin because carbohydrates aren’t accessible during the fasting periods, the body overproduces ketones. “The ketones from burning fat too quickly have built up in their system, and that could damage the kidneys and go to the brain and cause brain swelling,” Pupo says. Diabetic ketoacidosis may even lead to a diabetic coma or death.

For anyone, regardless of whether they have diabetes, cutting out meals and restricting entire food groups can furthermore cause nutritional deficiencies. Without enough nutrition, particularly protein, there’s also a risk for muscle mass loss. “When you really deprive the body of nutrients, your body not only breaks down fat but muscle as well. And our heart is a muscle,” Pupo says.

Steps to Take Before You Try the Popular Diet Plan

Talk to your doctor. Before starting an IF plan, talk to your doctor to come up with a safe approach and management plan for you, as well as to adjust any of your medication doses. Those people on insulin should be particularly careful: If you’re on it and restrict eating, you may be at a greater risk of low blood sugar, which can lead to life-threatening symptoms, such as dizziness, confusion, seizures, loss of consciousness, or even death, according to the American Diabetes Association. “Low blood sugar is very dangerous for a diabetic person,” Gandhi says.

Find a plan that works for you. Plans for IF vary from those that restrict calories two or three days a week and those that restrict eating to certain periods of the day to more strict plans that include fasting for up to 36 hours at a time for 7 or 14 days. The key is to find a plan that you can stick with for the long term.

Be prepared for side effects. It’s common to have headaches, cramps, constipation, or diarrhea, at least initially. “If you’re feeling very unwell, stop. You might be hungry, but you shouldn’t be lethargic or throwing up,” Dr. Fung says.

Eat healthily. Your diet should consist of whole, unprocessed foods, including nonstarchy vegetables, protein, and healthy fats, as well as a multivitamin and plenty of water to prevent dehydration and headaches. A healthy diet will help you lose or manage your weight and keep your blood sugar level steady.

Don’t skip breakfast. Always start the day with a diabetes-friendly breakfast within one to two hours of waking up. “Our blood sugar naturally rises in the morning — that’s how we wake up — and we don’t want that to be followed by a drop. We want to maintain a steady, stable blood sugar throughout the day,” Gandhi says.

Keep your expectations in check. An IF plan doesn’t work for everybody, and your medical team may not feel that it’s a good fit for you. It’s important to consult these professionals before giving IF a try, as going for long periods without eating when you have diabetes can be dangerous or, at the very least, not produce the results you want. “If you’re recommending something to a patient, you have to look at the whole picture and think, Can this fit into somebody’s life, will they be happy, and will the results outweigh the risks.” Gandhi says. “To me, the answer is no. You will see some weight loss, but it’s not going to be in a healthy way; it’s not going to be in a sustainable way.”

Get support. If you do get the all clear to try IF, experts advise following the plan with a friend or joining an online community or social network to help motivate you to stick with it.

Intermittent Fasting and Diabetes: The Bottom Line

Although IF may help you lose weight, which can help you better control diabetes, it’s important to consult your medical team. Together you can decide what’s most sustainable and safe for you as an individual. Due to the risk of potential blood sugar swings, full-blown IF may not be for you, especially if you aren’t controlling the diabetes well. Instead, decreasing your portion sizes, increasing your physical activity between meals, and making healthy food swaps — all of which align with IF — may be a better approach.

Intermittent Fasting and Diabetes: A Safe Eating Plan for People with Type 2?

Eating whatever you like for a few days; seriously cutting back on others can be effective for weight loss but is it harmful to people with diabetes? Here’s what experts say Written by Ilene Raymond Rush 17

Before you try intermittent fasting, you should be aware of the downsides. Experts recommend consulting with your doctor first, especially if you take medication to help control your blood sugar.

Intermittent fasting (IF), going without food for a period of time rather than reducing daily caloric intake, may be a good choice for people with type 2 diabetes.1 The eating plan, which has gained popularity over the past few years, has proven easier for some people to follow than calorie-restricted diets.

“It’s an ancestral way of eating,” says Linda Sartor, RD, MA, CDE, LDN, Diabetes Nutritionist, Penn Rodebaugh Diabetes Center at Penn Medicine. “Throughout millennia, man didn’t always have a constant supply of food, there were times of plenty and then nothing.”

“There is no one definition of intermittent fasting,” says Sartor, who has helped people with type 2 diabetes adapt to IF. “How to accomplish IF varies—some people eat 8 hours then fast while others eat normally five days a week and fast for two consecutive or non-consecutive days. Many people love the idea of eating only two meals a day, or—if fasting is too daunting—restricting yourself to 600 calories on fasting days, or simply not eating from 7 at night until 7 in the morning.”

Another approach is to try knocking off 600 calories from your daily intake. “For a man, who would normally eat 2000 calories, that would bring him down to 1400-1500; for a woman who would normally eat 1500 to 1800, it would knock down her intake to 1000 to 1200.” (For reference: One cup of high-end ice cream has about 600 calories; so do 2 slices of 14” pizza with pepperoni.)

“We used to recommend grazing for people with type 2 diabetes—three meals and three snacks a day—but that didn’t prove itself,” Sartor explains. “People tended to eat six meals. Now we say nothing after 7 pm unless you have a low blood sugar, which is a kind of IF. I’ve had a number of folks with type 2 in our practice who had safe and effective weight loss on IF. They lowered their A1C’s and some reduced or got off their medications.”

Possible Downsides to Intermittent Fasting for Diabetes

The biggest downside to intermittent fasting for people with type 2 is the danger of hypoglycemia or low blood sugar.2 For this reason, it is recommended that type 2s who wish to follow these diets consult with a nutritionist or their healthcare practitioner, both to carefully monitor their sugars and to adjust medications if hypoglycemia becomes an issue.

A recent study3 examined the dangers of low blood sugars while fasting, and found that while hypoglycemia was a risk when people with type 2 diabetes tried IF, “with education and medication reduction” fewer low blood sugar episodes occurred.

In the research, 37 participants were divided into two groups, one of which fasted on two nonconsecutive days and the other on two consecutive days over 12 weeks. Improvements were seen in weight, A1C, fasting glucose and quality of life for all participants, with an average rate of 1.4 hypoglycemic events for those on medications that produced hypoglycemia.

Occasionally skipping a meal won’t cause a problem for most people with type 2 diabetes, says Mario Skugor, MD, a clinical assistant professor of medicine at the Endocrine and Metabolic Institute, Cleveland Clinic. “There is no good reason they can’t in order to lose weight, but if you’re on a sulfonylurea skipping meals could cause lower blood sugars.”

“On the other hand, if you are on metformin, GLP-1s, DDP-4s or newer insulin analogs you can probably plan to skip a meal without giving yourself low blood sugar,” the endocrinologist says. “With the newer insulin, you don’t need to eat on a schedule, which is one of the advantages of modern medication.”

“But,” he cautions, “One diet is not any better than another.”

Small Study: More Evidence

Another small but recent Canadian study also found advantages of intermittent fasting for people with type 2 diabetes4.

Three men, aged between 40 and 67, tried intermittent fasting to see if it would improve their health and lessen their reliance on insulin and medication. The men had diabetes for varying amounts of time—between 10 and 25 years and were taking various drugs to control their disease as well as daily units of insulin. In addition to type 2 diabetes, they all had high blood pressure and high cholesterol.

One of the men fasted for three days out of the week; the other two fasted on alternate days for 24 hours. On fast days they were permitted very low callow-calorie, such as tea/coffee, water or broth, and one very low-calorie meal for dinner.

They all participated in a 6-hour long nutritional training seminar to become educated on the development of diabetes and it’s impact on the body as well as learning how diabetes can be managed through diet.

In less than a year of following a fasting routine, their average A1C levels, weight and waist circumference dropped to more healthy numbers. In addition, all three men were able to stop insulin injections within a month of starting their fasting schedule—in one case this took only five days. Two of the men were also able to stop taking their diabetic medication and the third man discontinued three of the four drugs he was taking.

Fasting Not Indicated for Everyone

Pregnant women are not advised to follow this regimen. And while fasting for type 2s may be beneficial, Sartor notes such a plan is much more tricky for people with type 1.

“Fasting leads to breaking down fat for fuel, which leads to more ketones in the bloodstream and can lead to diabetic ketoacidosis. Type 1s need very close monitoring to avoid this,” she says.

Benefits of IF

“Overall, IF has been shown to be good for the brain,” says Sartor. “It helps with mental clarity, boosts antioxidants, protects the body from free radicals, increases energy production in the mitochondria and helps with autoimmune diseases.”

“There is also lots of research that shows that IF in type 2 diabetes helps reduce insulin resistance, one of the major problems in people with type 2. IF helps people use insulin more efficiently,” she says. “While the literature is clear that any approach to losing weight lowers inflammation, IF seems also to decrease visceral fat which leads to fewer metabolic issues and a lower rate of heart disease.”

According to Amy Hess Fischl, MS, RD, LDN, BC-ADM, CDE a program coordinator for the Teen and Adolescent Diabetes Transition Program at the University of Chicago’s Kovler Diabetes Center, patients should not “jump in without consulting with a registered dietitian nutritionist.”

“For the newly diagnosed who are not on any diabetes medications or some people with prediabetes without other pre-existing conditions, intermittent fasting may help to jump start weight loss efforts,” says Hess-Fischl. “But each person should be assessed by an RDN to see if it’s the right option for them.”

“When it comes to nutrition, one size does not fit all.”

Updated on: March 28, 2019 View Sources

Linda Sartor, April 10th, 2018, phone
Mario Skugor, April 11th, 2018, phone
Amy Hess-Fischl, April 3, 2018, email

Continue Reading Type 2 Diabetes Oral Medications

There’s a ton of incredibly promising intermittent fasting (IF) research done on fat rats. They lose weight, their blood pressure, cholesterol, and blood sugars improve… but they’re rats. Studies in humans, almost across the board, have shown that IF is safe and incredibly effective, but really no more effective than any other diet. In addition, many people find it difficult to fast.

But a growing body of research suggests that the timing of the fast is key, and can make IF a more realistic, sustainable, and effective approach for weight loss, as well as for diabetes prevention.

The backstory on intermittent fasting

IF as a weight loss approach has been around in various forms for ages, but was highly popularized in 2012 by BBC broadcast journalist Dr. Michael Mosley’s TV documentary Eat Fast, Live Longer and book The Fast Diet, followed by journalist Kate Harrison’s book The 5:2 Diet based on her own experience, and subsequently by Dr. Jason Fung’s 2016 bestseller The Obesity Code. IF generated a steady positive buzz as anecdotes of its effectiveness proliferated.

As a lifestyle-leaning research doctor, I needed to understand the science. The Obesity Code seemed the most evidence-based summary resource, and I loved it. Fung successfully combines plenty of research, his clinical experience, and sensible nutrition advice, and also addresses the socioeconomic forces conspiring to make us fat. He is very clear that we should eat more fruits and veggies, fiber, healthy protein, and fats, and avoid sugar, refined grains, processed foods, and for God’s sake, stop snacking. Check, check, check, I agree. The only part that was still questionable in my mind was the intermittent fasting part.

Intermittent fasting can help weight loss

IF makes intuitive sense. The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains (think white flours and rice), are quickly broken down into sugar, which our cells use for energy. If our cells don’t use it all, we store it in our fat cells as, well, fat. But sugar can only enter our cells with insulin, a hormone made in the pancreas. Insulin brings sugar into the fat cells and keeps it there.

Between meals, as long as we don’t snack, our insulin levels will go down and our fat cells can then release their stored sugar, to be used as energy. We lose weight if we let our insulin levels go down. The entire idea of IF is to allow the insulin levels to go down far enough and for long enough that we burn off our fat.

Intermittent fasting can be hard… but maybe it doesn’t have to be

Initial human studies that compared fasting every other day to eating less every day showed that both worked about equally for weight loss, though people struggled with the fasting days. So, I had written off IF as no better or worse than simply eating less, only far more uncomfortable. My advice was to just stick with the sensible, plant-based, Mediterranean-style diet.

New research is suggesting that not all IF approaches are the same, and some are actually very reasonable, effective, and sustainable, especially when combined with a nutritious plant-based diet. So I’m prepared to take my lumps on this one (and even revise my prior post).

We have evolved to be in sync with the day/night cycle, i.e., a circadian rhythm. Our metabolism has adapted to daytime food, nighttime sleep. Nighttime eating is well associated with a higher risk of obesity, as well as diabetes.

Based on this, researchers from the University of Alabama conducted a study with a small group of obese men with prediabetes. They compared a form of intermittent fasting called “early time-restricted feeding,” where all meals were fit into an early eight-hour period of the day (7 am to 3 pm),or spread out over 12 hours (between 7 am and 7 pm). Both groups maintained their weight (did not gain or lose) but after five weeks, the eight-hours group had dramatically lower insulin levels and significantly improved insulin sensitivity, as well as significantly lower blood pressure. The best part? The eight-hours group also had significantly decreased appetite. They weren’t starving.

Just changing the timing of meals, by eating earlier in the day and extending the overnight fast, significantly benefited metabolism even in people who didn’t lose a single pound.

So, is this as good as it sounds?

I was very curious about this, so I asked the opinion of metabolic expert Dr. Deborah Wexler, Director of the Massachusetts General Hospital Diabetes Center and associate professor at Harvard Medical School. Here is what she told me. “There is evidence to suggest that the circadian rhythm fasting approach, where meals are restricted to an eight to 10-hour period of the daytime, is effective,” she confirmed, though generally she recommends that people “use an eating approach that works for them and is sustainable to them.”

So, here’s the deal. There is some good scientific evidence suggesting that circadian rhythm fasting, when combined with a healthy diet and lifestyle, can be a particularly effective approach to weight loss, especially for people at risk for diabetes. (However, people with advanced diabetes or who are on medications for diabetes, people with a history of eating disorders like anorexia and bulimia, and pregnant or breastfeeding women should not attempt intermittent fasting unless under the close supervision of a physician who can monitor them.)

4 ways to use this information for better health

  1. Avoid sugars and refined grains. Instead, eat fruits, vegetables, beans, lentils, whole grains, lean proteins, and healthy fats (a sensible, plant-based, Mediterranean-style diet).
  2. Let your body burn fat between meals. Don’t snack. Be active throughout your day. Build muscle tone.
  3. Consider a simple form of intermittent fasting. Limit the hours of the day when you eat, and for best effect, make it earlier in the day (between 7 am to 3 pm, or even 10 am to 6 pm, but definitely not in the evening before bed).
  4. Avoid snacking or eating at nighttime, all the time.


Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Internal Medicine, May 2017.

Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism. American Journal of Clinical Nutrition, January 2005.

The Obesity Code, by Jason Fung, MD (Greystone Books, 2016).

Intermittent fasting interventions for treatment of overweight and obesity in adults: a systematic review and meta-analysis. JBI Database of Systematic Reviews and Implementation Reports, February 2018.

Metabolic Effects of Intermittent Fasting. Annual Review of Nutrition, August 2017.

Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metabolism, May 2018.

A physician’s introduction to therapeutic fasting

An illustrative case study

A 38-year-old female presents to the clinic for a diabetes follow-up. She has had type 2 diabetes for 6 years and would like to lose weight, take less medication, and have better control of her diabetes.

The patient’s diabetes medications comprise 1000 mg metformin twice daily and 5 mg glipizide twice daily. She reports that she is trying to eat well, but dines out a few times a week, particularly when she is too busy to pack a lunch for work. On a typical dine-out day the patient will have:


  • Morning meal: A latte and pastry from the coffee shop
  • Evening meal: A dish she prepares from a recipe box delivery service (eg, Fresh Choice, Hello Fresh).

She checks her glucose twice per day and does not drop low. Morning readings are between 150 mg/dL and 190 mg/dL (8.3–10.6 mmol/L), evening readings are between 180 mg/dL and 210 mg/dL (10.0–11.7 mmol/L). In addition to her diabetes medications, the patient also takes 40 mg atorvastatin for hyperlipidemia and 20 mg lisinopril daily for hypertension. Her physical exam highlighted the following:

She has been reading about intermittent fasting and would like to try it, but would like the opinion of her physician before going any further. Below are some talking points that would be helpful to address with such a patient.

Is intermittent fasting safe?

Excluding specific conditions (see below), fasting is exceedingly safe. It has been practiced worldwide for millennia and is a facet of every major religious culture, including Judaism, Christianity, Islam, Hinduism, and Buddhism.

Anecdotally, concern has been expressed about the effect of entering “starvation mode,” a catabolic state in which the body ceases basal metabolic function, turning to muscle protein as a source of fuel. This, however, is physiologically inaccurate with intermittent fasts (for definition, see tables below). The opposite occurs: basal metabolic rate increases during a fasted state, and is accompanied by increases in serum levels of norepinephrine (noradrenaline) and growth hormone. This surge in sympathetic hormones might interfere with patients’ sleep, which may be advised.


Hypoglycemia is a risk for patients who take insulin or sulfonylureas. In these cases, careful review of self-monitored blood glucose before fasting is recommended. Diabetes medication may need to be reduced or withheld during fasting periods to minimize the risk of hypoglycemia.

Does intermittent fasting work?

Both intermittent fasting and time-restricted feeding (see below) have demonstrated efficacy in reducing weight, central adiposity, and HbA1c in clinical trials ranging from 8 to 52 weeks. There is also evidence that intermittent fasting and time-restricted feeding improve insulin sensitivity as well as biomarkers relating to cardiovascular disease such as blood pressure and resting heart rate.

A therapeutic fasting regimen in patients with type 2 diabetes is also a known strategy for de-prescription and inducing disease remission.

Ongoing research is exploring the relationship between periods of fasting and improved immune function, increased longevity, treatment for chronic neurological disorders, enhanced cognitive performance, and more.

How does intermittent fasting work?

We have evidence that molecular and biochemical networks are affected by fasting. These findings are beyond the scope of this synopsis.

Type 2 diabetes is a bodily state of hyperinsulinemia. The key to fasting is reducing insulin: the primary anabolic (and anti-catabolic), obesogenic, and glycogenic hormone. Frequent meals – especially those of a “typical” North American diet – maintain high levels of insulin, rendering the body perpetually anabolic and dependent on glucose for energy. Periods of fasting “flip the metabolic switch,” allowing the body to mobilize stored fats to use for energy via fatty acid and ketone oxidization. This counter-regulatory surge is driven by glucagon, glucocorticoid, and catecholamine hormones.

Continuous caloric restriction – that is, traditional dietary advice – fails to enable the release of counter-regulatory hormones. This results in a failure to mobilize energy from fat. Energy restriction without access to adipose storage results in the classic dieter’s scenario: hungry, fatigued, and irritable. The cyclical nature of feasting and fasting allows the body to oscillate between glucose and fatty acids for energy, avoiding the unfavorable effects of a continuous reduced-calorie approach. It is conceivable that evolutionary processes adapted the plasticity of the human body for these cycles of feasting and fasting.

Indications and contraindications of intermittent fasting

As mentioned, fasting is safe. It can be used to improve symptoms related to disease or as primary prevention. Many people use intermittent fasting to optimize performance (and/or aesthetics), as fatty acid and ketone oxidation allow for retention of lean body mass while reducing adiposity.


Those who should not fast include:

  • pregnant or breast-feeding women children
  • people with a history of eating disorders or body dysmorphic disorder
  • patients with cachexia, advanced liver or kidney insufficiency, hyperthyroidism, or advanced cerebrovascular insufficiency or dementia (Source)

People with chronic disease should seek medical advice before starting a fasting program, and precautions should be taken in patients who are fasting while on hypoglycemic medications.

What’s the best way to start intermittent fasting?

In short, there isn’t one. However, an advantage of fasting is its flexibility: it can be used to complement any diet and can be adjusted to fit an individual’s lifestyle. Popular methods include the following:

Type of fast

Fast regime

12-hour fast

Eat only within a 12-hour window daily

16-hour fast

Eat only within an 8-hour window daily

24-hour fast

Eat one meal per day

5:2 fast

Eat normal meals 5 days of the week, reduce caloric intake to <500 on two days

Alternate day fast

Eat normal meals every other day

Longer fasts

These vary; one option is to fast for 5 consecutive days every 3 months

Finding a method that works for your patient is critical for adherence. Experiencing hunger is common and benign, especially at the beginning, but fatigue, dizziness, and other systemic symptoms are more worrisome and warrant breaking of a fast.


How long should patients commit to intermittent fasting?

The length of a fasting regimen will depend on multiple factors including patient and physician goals (eg, weight loss, de-prescription, cardiovascular health, performance, general wellness).

A distinct advantage to fasting that can promote long-term adherence is its adaptability. Fasting can accompany any diet and fits into a variety of schedules. It is unique from other diets in its low-maintenance, no-cost character: specific foods are not required to prepare, meal replacements do not mandate purchase, and no additional time is required to adhere to a fasting regimen.

While religious practices have incorporated fasting for millennia, clinical trials on fasting protocols range from 8 to 52 weeks. Case series report de-prescription from insulin within weeks to months, and show fasting regimens to be well-tolerated over several months.


With few exceptions, structured fasting is a safe and effective dietary strategy for patients with type 2 diabetes. Type 2 diabetes is characterized by hyperinsulinemia. Fasting results in a reduction of endogenous insulin, an anabolic hormone that prevents lipolysis. Reduction of insulin enables a “metabolic switch” for the body to undergo lipolysis for energy production, physiology not created by standard dietary advice of continuous caloric restriction. Fasting protocols have been shown to reduce HbA1c, central adiposity, and weight, and to improve insulin sensitivity and cardiovascular disease risk factors.


Back to the case

This patient has an interest in time-restricted eating. Her motivations at this point are simple and straightforward: weight loss, improved glycemic control, and fewer medications. She appears to have good renal function (eGFR = 84 mL/min per 1.73 m2). Based on her current schedule, she will benefit from excluding her high-calorie, high-carbohydrate morning meal.

First, thank the patient for researching ways to be in control of her health. A 16-hour daily fast would work with her current schedule: she could fast during her non-nutritive eating period, eliminating the morning latte and pastry. She is taking glipizide, a sulfonylurea, so careful consideration to avoid hypoglycemia should be taken. At a minimum, she should reduce the dose to once daily in the morning. Over time, there is a possibility that she could discontinue taking glipizide altogether. Metformin can be continued, but dosage timing could change to be taken with food if she experiences gastrointestinal upset when taken on an empty stomach. We would recommend encouraging the patient to return with any questions or concerns.

About the authors

Jay Shubrook

Jay H Shubrook, DO, is a Board-Certified Family Physician and Diabetologist. He is a Professor in the Primary Care Department at the Touro University California College of Osteopathic Medicine. Disclosures

Read his full bio

Jamie Katuna

Jamie Katuna is a DO/MPH candidate in her third year at Touro University California College of Osteopathic Medicine. Disclosures

Read her full bio

Promising approach: Prevent diabetes with intermittent fasting

Fatty liver has been thoroughly investigated as a known and frequently occurring disease. However, little is known about excess weight-induced fat accumulation in the pancreas and its effects on the onset of type 2 diabetes. The research team led by Professor Annette Schürmann and Professor Tim J. Schulz of the German Institute of Human Nutrition (DIfE) has now found that overweight mice prone to diabetes have a high accumulation of fat cells in the pancreas. Mice resistant to diabetes due to their genetic make-up despite excess weight had hardly any fat in the pancreas, but instead had fat deposits in the liver. “Fat accumulations outside the fat tissue, e.g. in the liver, muscles or even bones, have a negative effect on these organs and the entire body. What impact fat cells have within the pancreas has not been clear until now,” said Schürmann, head of the Department of Experimental Diabetology at DIfE and speaker of the German Center for Diabetes Research (DZD).

Intermittent fasting reduces pancreatic fat

The team of scientists divided the overweight animals, which were prone to diabetes, into two groups: The first group was allowed to eat ad libitum — as much as they wanted whenever they wanted. The second group underwent an intermittent fasting regimen: one day the rodents received unlimited chow and the next day they were not fed at all. After five weeks, the researchers observed differences in the pancreas of the mice: Fat cells accumulated in group one. The animals in group two, on the other hand, had hardly any fat deposits in the pancreas.

Pancreatic adipocytes mediate hypersecretion of insulin

In order to find out how fat cells might impair the function of the pancreas, researchers led by Schürmann and Schulz isolated adipocyte precursor cells from the pancreas of mice for the first time and allowed them to differentiate into mature fat cells. If the mature fat cells were subsequently cultivated together with the Langerhans islets of the pancreas, the beta cells of the “islets” increasingly secreted insulin. “We suspect that the increased secretion of insulin causes the Langerhans islets of diabetes-prone animals to deplete more quickly and, after some time, to cease functioning completely. In this way, fat accumulation in the pancreas could contribute to the development of type 2 diabetes,” said Schürmann.

Significance of pancreatic fat for diabetes prevention

Current data suggest that not only liver fat should be reduced to prevent type 2 diabetes. “Under certain genetic conditions, the accumulation of fat in the pancreas may play a decisive role in the development of type 2 diabetes,” said Schulz, head of the Department of Adipocyte Development and Nutrition. Intermittent fasting could be a promising therapeutic approach in the future. The advantages: it is non-invasive, easy to integrate into everyday life and does not require drugs.

Intermittent Fasting

Intermittent fasting means not eating during certain time slots. However, water, unsweetened tea and black coffee are allowed around the clock. Depending on the method, the fasting lasts between 16 and 24 hours or, alternatively, a maximum of 500 to 600 calories are consumed on two days within a week. The best known form of intermittent fasting is the 16:8 method which involves eating only during an eight-hour window during the day and fasting for the remaining 16 hours. One meal — usually breakfast — is omitted.

Islets of Langerhans

The islets of Langerhans — also referred to as islet cells or Langerhans islets — are islet-like accumulations of hormone-producing cells in the pancreas. A healthy adult has about one million Langerhans islets. Each “islet” has a diameter of 0.2-0.5 millimeters. The beta cells produce the blood glucose-lowering hormone insulin and make up about 65 to 80 percent of the islet cells. When blood glucose levels are elevated, these secrete insulin into the bloodstream so that the levels are normalized again.

The 5:2 intermittent fasting (IF) diet, more commonly referred to simply as the 5:2 diet, has become one of the more popular diet plan in recent years.

Studies have shown that the diet helps with weight loss and may also reduce insulin resistance, both of which are of particular interest for many people with type 2 diabetes or borderline diabetes .

One reason for the popularity of the diet is that it allows a certain amount of flexibility, in comparison to low calorie diets, on most days of the week.

Theory behind the diet

The idea of the diet is that short periods of fasting prompt the body to repair damage but not enter a starvation mode of conserving energy.

Whilst the theory has yet to be conclusively proved, clinical studies have shown promising results for the diet, however it has only been examined over relatively short time spans, of less than a year.

How the 5:2 diet works

The 5:2 intermittent fasting diet is based on a simple idea. 5 days a week you stick to meeting the daily calorie intake advised for people of a healthy weight, that being:

  • 2,500 kcal per day for men
  • 2,000 kcal per day for women

For the other 2 days each week, the diet stipulates that you have only around 25% of the values above, which is equal to:

  • 600 kcal on these days for men
  • 500 kcal on these days for women

The fasting days can be taken at any time during the week as long as you do not take 2 fasting days consecutively.

Benefits of the 5:2 diet

Clinical studies have shown that the benefits of intermittent fasting are largely similar to those of a calorie restricted diets .

The most commonly reported benefits among people from following the 5:2 diet:

  • Weight loss
  • Decreased levels of triglycerides and LDL cholesterol
  • Reduced blood pressure
  • A reduction in insulin resistance

Research has shown that periods of fasting can help to improve life expectancy and decrease risks of diseases including nerve disorders, Alzheimer’s disease and cancer. However, whether these benefits apply to a 5:2 fasting diet cannot be confirmed as long term clinical studies have yet to be performed.

Is the 5:2 fast diet safe for diabetes?

Whilst shorter term studies have displayed promise for intermittent fasting diets, long-term safety of the 5:2 diet is yet to be determined.

As with any diet plan, you should always consult your GP or diabetes health team before making any significant changes to your diet as they could affect blood glucose levels or impact on your medication.

Type 2 diabetes and the 5:2 fast diet

The fact that intermittent fasting shows evidence of improving insulin sensitivity may be an attractive option for people with a BMI over 25, borderline diabetes (prediabetes) or with type 2 diabetes but not on blood sugar-lowering medications .

The diet may be good for people who can handle single days of significantly restricted calorie intake in preference to modest calorie restriction every day.

On fasting days, the body will be forced to use stored energy from the body, fat and stored sugar (glycogen), which can help with weight loss and may improve blood glucose and cholesterol levels.

If you are on insulin, or hypo causing medication, such as sulphonylureas or glinides, an intermittent fasting could significantly increase the risk of hypos. Your doctor should advise you on whether the diet is appropriate.

Type 1 diabetes and intermittent fasting

If you have type 1 diabetes, following a 5:2 diet could make diabetes management more difficult to achieve and could significantly increase the risk of hypoglycemia .

If your health team are happy for you to start an intermittent fasting diet, they may wish to monitor you more closely to reduce the likelihood of hypoglycemia or increased ketone levels occurring.

What evidence is there of the benefits of this diet?

A study published in 2010 reviewed 107 women, between the ages of 30 and 45, with BMI values ranging between 24 and 40.

The participants were randomly assigned to one of two diets, either continuous energy restriction (CER) or intermittent energy restriction (IER). The CER dieters had a reduced calorie intake of 1,500 kcal through the week, while the IER diet group followed the 5:2 fasting plan.

At the end of the study, both sets of dieters lost a similar amount of weight on average, and similar improvements were also seen in levels of triglycerides, LDL ‘good’ cholesterol and blood pressure.

One area, however, where intermittent fasting was shown to be stronger than continuous calorie restriction was in reducing fasting insulin levels and insulin resistance.

How to follow the 5:2 diet

Depending on your outlook, the 5:2 diet may be seen as more or less practical than a continuously reduced calorie diet.

The benefit being that on most days you needn‘t consume less than the daily recommended calorie limit. However, some people may find that calorie intakes of 500 or 600 calories a day are too low to be practical.

For best results, it’s recommended to follow basic healthy eating rules, such as having a good intake of vegetables, fruit, and limiting intake of processed foods where possible.

During the fasting days, you will need to rely on very low calorie meals to stay within the daily 500 or 600 calorie counts.

5:2 diet fasting day meal ideas

An example of good meal picks on fasting days include those based low fat foods such as:

  • Eggs (65 kcal per medium egg)
  • Grilled chicken breast without the skin (190 kcal per 100g)
  • Prawns (105 kcal per 100g)
  • Non-battered white fish (135 kcal per 100g)

Vegetables tend to be low calorie but if you need very low calorie vegetables, the following vegetables are particularly good options:

  • Cucumber (15 kcal per 100g)
  • Celery (20 kcal per 100g)
  • Bell pepper (26 kcal per 100g)

Intermittent fasting has a lot of promise for weight loss – partly because the fasting itself has beneficial effects, and partly because it’s just an easier way of reducing calories without having to count and measure and track. “Eat only between noon and 7pm” is a whole lot easier to manage than “eat 1500 calories per day.”

But what about metabolic problems that are related to weight gain but not quite the same? Here’s a look at intermittent fasting and type 2 diabetes (T2D) – does it help protect people at risk from developing the disease, and is it safe for people who are already diabetic?

1. There’s quite a bit of evidence in favor.

Intermittent fasting has been studied pretty extensively for weight loss, but there are also some studies specifically on people with T2D. For example, this study explored an IF (4-8 hour feeding window per day) intervention in 10 adults with Type 2 diabetes, focusing on whether or not the patients could put up with it and whether it was safe. And it turns out it worked pretty well: the patients had lower morning blood sugar during the IF intervention, and fewer blood sugar spikes after meals.

Another group of researchers compared IF (fasting 2 days/week) to ordinary calorie restriction for people with T2D. Their results showed that both diets delivered comparable improvements in blood sugar control and weight. And a review of multiple studies comparing regular calorie restriction to intermittent or alternate-day fasting confirmed the value of the IF/ADF approach for managing blood sugar.

For folks more interested in prevention than treatment, another study in overweight women at risk of developing T2D found that intermittent energy restriction (very low-calorie diet 2 days/week) and continuous calorie restriction (moderately low-calorie diet all the time) caused the same amount of weight loss, but the intermittent restriction improved insulin sensitivity more.

And here’s an interesting case report. A case report is basically the story of one individual patient. In this case, the guy spent 4 months on IF. His technique was to do a 24-hour fast three times a week, but over the 4 months of the study, he slowly lengthened the fasting period until he was fasting for nearly 2 full days twice a week. By the end, he’d dropped 17% of his body weight, dramatically improved his long-term blood sugar control, and gotten off all his meds. As the case report noted: “The patient did not find it difficult to adhere to the fasting schedule and did not experience any hypoglycaemic episodes or other significant adverse effects.”

How does it work? Partly, it’s just the calorie restriction, but the fasting itself also does have something to do with it. For example, this paper, in mice with obesity-induced diabetes, found that intermittent fasting improved survival of beta cells in the pancreas. Those are the cells that produce insulin, so by improving beta cell survival, IF helped the mice regulate insulin and blood sugar more tightly. Not a bad benefit for just…not eating.

2. Some studies suggest it may also alleviate secondary effects

Most of the studies above focused on blood sugar regulation and insulin sensitivity – which, after all, are the main issues that define diabetes. But other research indicates that intermittent fasting may also be helpful for other symptoms and consequences of T2D. For example, diabetic retinopathy (vision issues) may respond to IF, at least in mice. The researchers who did that study found that IF actually helped with diabetic retinopathy by modifying the gut biome. Specifically, IF increased the levels of certain beneficial bacterial species, which caused the mice to make more of a bile acid called tauroursodeoxycholate (TUDCA). TUDCA is neuroprotective and may have protected retinal cells in the eyes against damage. One commenter on the article noted that:

“As the TUDCA TGR5 receptors are present in neural cells, it is tempting to speculate that intermittent fasting could also have the potential to improve other diabetic microvascular complications, in particular diabetic neuropathy. The most important question, however, is whether and to what degree could such a concept be extrapolated to humans.”

3. Research on people taking meds: reason to be cautious

One major potential problem with IF is that people who take insulin or other drugs to manage diabetes might need to take special care in adjusting their medications. As this study found, patients on an intermittent fasting protocol did have a higher risk of hypoglycemic events, compared to patients on a standard calorie-reduced diet. Even when they reduced blood-sugar lowering medications, they still had an average of 1.4 hypoglycemic events over the 12-week study. The researchers did still confirm that fasting lowered fasting blood sugar and improved long-term blood sugar control, but this indicates that it might also have significant risks.

Another review describes medication changes required or tested for patients taking insulin and other hypoglycemic drugs. The study does describe the protocol in detail, but it’s really complicated and depends on regular, accurate blood sugar readings.

Basically, if you take blood sugar lowering meds, the Paleo approach to intermittent fasting is to talk to your doctor, the reasonable approach to intermittent fasting is to talk to your doctor, and the best approach to IF for weight loss is to talk to your doctor.

4. There are lots of schedule options.

The studies above used all kinds of protocols – from restricted feeding windows every day to two days a week of semi-fasting (~500 calories/day) to longer fasts of 1-2 full days. There are a lot of options and all of them seem to have some benefits.

Restricted feeding windows: this is when you set a certain amount of time every day to eat and fast for the rest of the day. Many people choose the afternoon and evening, but this study in patients with Type 2 Diabetes showed successful results with patients eating only breakfast and lunch (and then fasting during the late afternoon and evening).

One-day (24-ish hour) fasts: a few of the successful studies above used one or more full-day fasts per week (or “fasts” that involved only a few hundred calories on the “fast” day).

Longer fasts: This study even used a “fasting” protocol that involved 7 straight days of 300 calories/day, which is really stretching the limit of what you could consider “intermittent” or “fasting,” but they had great results with it in patients with type 2 diabetes, especially for blood pressure.

It almost seems like any kind of eating schedule that gets people to stop eating sometimes is pretty good for us – which is great, because then everyone can pick an eating pattern that works with their work schedule and preferences.

Have you tried intermittent fasting for better blood sugar control? How did it work out? Rants or raves to share? Let us know on Facebook or Twitter!

Is Intermittent Fasting Good for Someone with Type 2 Diabetes?

With Caroline Apovian, MD, FACP, FACN; Scott Isaacs, MD, FACP, FACE; and, Angela Fitch, MD, FACP

Eat all that you want one day, cut way back the next. This so-called intermittent fasting diet seems to be trending. It may sound like a great way to lower your hemoglobin A1c as the pounds melt off. But is it a good idea?

A new study from New Zealand suggests it might be, while three US doctors who reviewed the findings for EndocrineWeb urge caution, saying there are much better ways to achieve a healthy weight.

The New Zealand researchers found the risk of low blood sugar (hypoglycemia) was increased during the fasting days, as expected, but that the two intermittent fasting plans they tested still managed to produce weight loss and a drop in A1c levels, which is used to assess your risk for diabetes;1 the study is published in Diabetic Medicine.

However, three endocrinology experts who reviewed and commented on the study for EndocrineWeb say other approaches are less hazardous and just as, or more effective in producing a healthy weight loss.

Evaluating the Research on Intermittent Fasting

Researchers from Wellington Hospital and the University of Otago in New Zealand defined intermittent fasting a bit differently than we do here in the US. Participants could eat whatever they wanted five days a week and then they were instructed to fast for the next two days.1 They had to do this for 12 weeks. In this study, the ”fast” was actually a very low-calorie diet. Men could eat about 600 calories on a “fast” day and women were limited to 500 calories.

At the start, 41 participants who had been living with type 2 diabetes (T2D) for years were randomly assigned to this 5:2 plan, as it is sometimes called. About half of them were instructed to fast for two days in a row during the week; the others were instructed to fast on non-consecutive days.

In the consecutive fasting group, the average age was 62 years and their diabetes diagnosis had been made 13 years ago, on average. In the non-consecutive group, the average age was 58 years, and their diagnosis had been made 9 years earlier.1

The men and women were on a variety of medications, including insulin, sulfonylureas, metformin, and oral hypoglycemic agents.1 The researchers made adjustments to their medications in response to lower blood sugar levels on the fasting days, to avoid worrisome hypoglycemic episodes. The main study aim was to look at low blood sugar events and to monitor the amount of weight loss, A1c levels, and other parameters.1

Implementing the Intermittent Fasting Study

In all, 15 participants experienced low blood sugar events, for a total of 53 such incidents. The rates of low blood sugar were no differences between the consecutive and non-consecutive groups, but the chance of having low blood sugar was doubled on fasting days than on non-fasting.

Both groups lost weight. At the study start, the group that fasted on non-consecutive days weighed, on average, 242 pounds. By the end of the 12-week study, they had lost on average of 8 pounds. Those in the consecutive fasting group weighed, on average, 239 pounds at the study start, and by the end, they had lost nearly 7 pounds on average, which isn’t statistically significant meaning both groups had similar results.

The level of A1cs declined from 8.2 to 7.5 in the non-consecutive group and from 8.4 to 7.8 in the consecutive fasting days group; also not significantly different.

The final answer on the worth of this approach is still up for debate, the researchers write, “Our study protocol could be adopted for the longer-term studies that will be required to assess the tolerability and sustained efficacy of an intermittent fast.”1 Unfortunately, they didn’t respond to our questions about how the groups differed and whether any of the participants were willing to stay with the diet long-term.

Intermittent Restricted Calorie Dieting Not Encouraged

While the study demonstrates that the following a very low-calorie diet can be safe for those with type 2 diabetes, at least for 3 months, it is ”not very effective,” says Scott Isaacs, MD, FACP, FACE, an endocrinologist and adjunct instructor of medicine at Emory University School of Medicine, in Atlanta.

“The study showed minimal weight loss over the 12-week period of about 6 to 7 pounds, which is less than the typical weight loss on a standard low-calorie diet,” Dr. Isaacs says. His advice: “Focus on a healthy low-calorie meal plan instead. Clearly following a low-calorie meal plan every day is superior to being on a very low-calorie diet for two days out of the week.”

Angela Fitch, MD, FACP, associate professor of internal medicine and pediatrics at the University of Cincinnati College of Medicine/UC Health, says that while intermittent fasting can be an option, patients who choose this approach must work closely with their doctors to figure out how best to lower their hypoglycemic medications on fasting days.

Overall, however, Dr. Fitch says, “the most consistent way to lose weight and keep it off when you have type 2 diabetes is limiting the carbohydrates in your diet.” Eating less than 150 grams of starchy carbs a day improves blood sugar levels and helps to promote weight loss for most people with T2D, she says. Eating less than 20-50g is even better, but harder to maintain long-term, she says.

The quality of those carbs is crucial, she says. She advises eating carbohydrates with higher fiber content. Choose cauliflower, for instance, not white rice.

Despite the findings that the intermittent fasters lost some weight loss and lowered their A1c levels, the study did find a higher risk of hypoglycemia on the fasting days, points out Caroline Apovian, MD, FACP, FACN, professor of medicine and pediatrics at the Boston University School of Medicine and director, Center for Nutrition and Weight Management, Boston Medical Center.

“The reason is people on insulin and sulfonylureas really cannot safely do intermittent fasting is because of the risk of hypoglycemia,” she tells EndocrineWeb.

With any of my patients who choose to follow a low-calorie diet, Dr. Apovian warns them that they will need to see her often to monitor their gluocose levels and to adjust their medications, and they will need to check their blood sugars 3 times a day to avoid the risk of hypoglyemia.

None of the researchers or physicians interviewed have any financial conflicts.

Last updated on 01/23/2019 Continue Reading Best Diet for Weight Loss, Your Choice: Low Carb vs Low Fat View Sources

  1. Corley BT, Carroll RW, Hall RM, Weatherall M, Parry Strong A, Krebs JD. Intermittent fasting in Type 2 diabetes mellitus and the risk of hypoglycaemia: a randomized controlled trial. Diabetic Medicine. 2018. Ahead of print. Available at: Accessed February 26, 2018.

Fasting Blood Tests Can Be Dangerous for People with Diabetes

While more referrals to certified diabetes educators would help, Schwartz says they would still need an order from the prescribing doctor to make changes in insulin doses.

Regardless, eating food prior your blood draw is also an option, but what you choose to eat matters.

“If you are going to avoid fasting, it still matters what you choose for breakfast because a meal high in saturated fat can throw off some of your results,” said Schwartz. “Talk to your doctor about having a serving of fruit or something similarly healthy to prevent low blood sugars before having blood drawn.”

On the other hand, high blood sugar levels can also occur in patients with type 1 diabetes who skip breakfast because of the normal physiological reaction from the liver to release glycogen and convert it to glucose for the body to use as fuel.

While this process can occur in people without diabetes, too, a healthy pancreas compensates for this by releasing a small bolus of insulin. In a person with type 1 diabetes, this response is hard to predict and hard to dose for unless they’ve had time to experiment safely through trial and error.

But for many, fasting for the sake of blood tests should simply be avoided, because making the necessary adjustments in a patient’s usual medication regimen could complicate their diabetes management later in the day.

The safest bet for avoiding low blood sugars on the morning before a blood draw? Talk to your doctor about the idea of eating a small and healthy breakfast before heading out the door.

Ginger Vieira is an expert patient living with type 1 diabetes, celiac disease, and fibromyalgia. Find her diabetes books on Amazon and connect with her on Twitter and YouTube.

Diabetes Forecast


Whether you are honoring an ancient religious practice or heading to the lab for a fasting blood test, care is needed when missing meals with diabetes. Fasting can throw off the delicate balance of food, water, and blood glucose levels in potentially harmful ways.

Safety First

Fasting with diabetes poses significant risks, says Kathaleen Briggs Early, PhD, RD, CDE, of the Pacific Northwest University of Health Sciences. Most of the research on fasting and diabetes surrounds Ramadan, the annual Islamic observance that requires fasting from sunrise to sundown for 29 or 30 days. A commentary published in 2010 in Diabetes Care developed in collaboration with the American Diabetes Association (ADA) focused on fasting during Ramadan, though many of the issues it raises are relevant to other types of fasting as well. It says that “most often, the medical recommendation will be not to undertake fasting” if you have diabetes.

The paper acknowledges that fasting for spiritual reasons is a personal decision, but one that should include the guidance of a health care provider. A study found that 43 percent of people with type 1 diabetes and 79 percent of people with type 2 diabetes from 13 Islamic countries fast during Ramadan. With that reality, fasting safely becomes a priority for people with diabetes and their care providers.

“Anybody with diabetes needs to first talk to their doctor about going on a fast,” says Early, and some experts recommend a pre-fasting medical assessment to help ensure safety. If you are considering fasting, talk to your health care provider about a plan that takes medication, nutrition, and hydration into account. Regularly monitoring blood glucose during fasting is key to avoiding health emergencies.

Health Risks

Not eating when taking insulin or certain other diabetes medications can raise the risk of hypoglycemia (low blood glucose). A study of people with diabetes who fasted during Ramadan found that the risk of being hospitalized for hypoglycemia increased by 4.7-fold in people with type 1 diabetes and by 7.5-fold in those with type 2.

Pregnant women and people with a history of hypoglycemia, ketoacidosis (a complication of very high blood glucose), or poor blood glucose control are also considered very high risk. Heavy manual labor and illness may put a person into this group. For religious fasts that require abstinence from water, such as Ramadan, dehydration can raise the risk for serious complications among susceptible people, such as those with kidney or heart disease. “In extreme cases, electrolytes can get out of whack and exacerbate problems,” says Early.

High blood glucose can also be an issue during fasting. People often cut back on medication while fasting to lower the risk of hypoglycemia. With no food, the liver releases stored glucose for energy. Both of these contribute to high blood glucose. In one study, researchers found a fivefold increase in severe hyperglycemia in people with type 2 who fasted during Ramadan and a threefold increase in people with type 1.

Breaking the Fast

Perhaps the most important part of fasting with diabetes is knowing when to quit. Experts recommend always and immediately ending a fast if hypoglycemia (usually defined as a blood glucose level less than 70 mg/dl) occurs. In the case of a low, it’s important to break the fast and treat the low with food or drink that contains carbohydrate

Fasting should also cease with blood glucose levels above 300 mg/dl. Some other signs that it’s time to quit may include “common sense kinds of things,” says Early, so listen to your body. For example, if your urine becomes dark, that’s a sign you’re becoming really dehydrated. “Severe headache, nausea, and vomiting would all be signs that you’d want to break your fast,” says Early. Religious leaders tend to agree that fasts are not meant to create undue hardship or create a life-threatening situation. Finding a deeply meaningful spiritual experience can come from other sources beyond those that put you at risk.

Facets of Fasting

Plan with your provider how to handle these common situations involving fasting

Physiological Fast

Sometimes when doctors talk about a “fast,” they just mean the period that you aren’t eating while you sleep. For example, fasting blood glucose indicates first thing when waking up.

Fasting for Religion

Many religions include fast days, and the methods of fasting vary widely depending on religious observation. Some types of fasts may involve abstaining from food and water for a day or more, while others may require that a particular substance, such as oil or alcohol, be avoided.

Fasting for Medical Reasons

Surgeries and other procedures that require a general anesthetic often require a person to fast due to the risk of inhaling or choking on partially digested food during the procedure; water, however, may be allowed. Some blood tests, such as those for cholesterol, may require a person to not eat for 8 or 12 hours.

Fasting for Health

Some evidence suggests that fasting every other day can have health benefits similar to calorie restriction, though long-term studies have not yet been done. So-called “cleanses” and other fast-like practices are popular in alternative medicine as a way to “detoxify” the body, though scientific evidence does not support this practice.

The Unintended Fast

Sometimes missing a meal happens unintentionally because a person becomes distracted and forgets to eat or is without money to pay for food.

Finding Her Own Meaning

A young woman with diabetes comes to terms with fasting
Yom Kippur is the Day of Atonement, the holiest day of the year in Judaism. Yom Kippur requires an absolute fast: no food and not even a sip of water from sundown to sundown, plus a little extra (oy vey), to last around 25 hours. It can get pretty intense by the end, and, for people with diabetes, it may not be safe to participate. But that’s OK.

“In Judaism, if there is even the slightest doubt about health or if safety is an issue … you may not ,” says Gil Steinlauf, senior rabbi of Adas Israel Congregation in Washington, District of Columbia (full disclosure: my rabbi). A Hebrew phrase sums up this principle nicely: Pikuach Nefesh (Saving a Life), interpreted as the idea that most of Jewish law should be set aside to preserve human life. Other religions also typically allow people with certain health conditions to skip the religious observance of fasting.

Steinlauf’s younger daughter, Meirav Steinlauf, knows about Pikuach Nefesh firsthand. She was diagnosed with type 1 diabetes in early 2009. Meirav, 14, had her bat mitzvah last year and is now, according to the Jewish faith, herself accountable for upholding Jewish law. She did try once since her diagnosis to fast on Yom Kippur, but it didn’t go so well. “We were never going to let her do an all-day fast,” says Steinlauf. “She actually decided not to eat breakfast, and by 11 a.m. she was really sick.” So, per Pikuach Nefesh, that was the end of that.

Still, Meirav is determined “to give the day meaning.” Now, on Yom Kippur, she eats, she says, as though down with flu, having small portions of sick day–friendly foods, such as toast, and avoiding dessert. Because of the altered eating pattern, Meirav checks her blood glucose more often than normal. If she goes low, “I won’t have jelly beans,” and instead raises her blood glucose with a less-appealing source of carbohydrate. “I want, not to suffer,” she says, “but I want to understand why I fast.”

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