Low fat diet benefits

Fat Grams – How Much Fat Should You Eat Per Day?

Fatty acids are grouped according to the number of double bonds between carbons in their structures.

Monounsaturated Fat

Monounsaturated fatty acids (MUFAs) have one double bond in their carbon chains.

MUFA food sources are typically liquid at room temperature and fairly stable for cooking purposes.

The most common MUFA is oleic acid, which olive oil contains in high amounts.

Monounsaturated fat is linked to several health benefits, including a reduced risk of serious diseases such as heart disease and diabetes (5, 6, 7).

One review of 24 controlled studies found diets in monounsaturated fat lead to significantly lower blood sugar, triglycerides, weight and blood pressure, compared to high-carb diets. They also increased HDL (“good”) cholesterol levels (7).

MUFAs may also increase feelings of fullness that lead to reduced calorie intake.

In one study, people felt fuller and took in fewer calories for the next 24 hours after consuming bread rich in oleic acid, compared to bread that contained less (8).

Polyunsaturated Fat

Polyunsaturated fatty acids (PUFAs) contain two or more double bonds.

They can be divided into groups depending on the location of the double bonds. These include omega-3s and omega-6s.

These double bonds make PUFAs more flexible and fluid than saturated fats.

On the other hand, they’re also far more prone to damage and rancidity.

Studies have found that long-chain omega-3 fats have benefits for inflammation, heart disease, diabetes, depression and other health conditions (9, 10, 11, 12).

Although you need some omega-6 fats, they can be inflammatory when consumed in excess, especially if omega-3 PUFA intake is low (13, 14, 15).

Omega-6 fats are very common in modern-day diets. On the other hand, omega-3 fats are usually consumed in much smaller amounts.

Significantly, researchers report that the evolutionary diet of humans provided a ratio of omega-6 to omega-3 fats between 1:1 and 4:1. By contrast, it’s estimated that most people now consume these fats in a 15–17:1 ratio (16).

Saturated Fat

Saturated fatty acids (SFAs) have no double bonds in their carbon chains, so the carbons are said to be “saturated” with hydrogen.

They are very stable at high temperatures and far less likely to be damaged during cooking than polyunsaturated fats.

SFA intake can raise LDL (“bad”) cholesterol levels in some people, although this depends in part on the specific fatty acids consumed. It should also be noted that HDL cholesterol typically goes up as well (17).

Overall, research indicates that SFA consumption has a neutral effect on health and doesn’t appear to cause or contribute to heart disease (18, 19, 20).

In fact, some foods high in saturated fat may benefit metabolic health.

For example, studies suggest that the medium-chain triglycerides in coconut oil and palm oil may boost metabolic rate and reduce calorie intake (21, 22).

Trans Fat

In a trans fats molecule, hydrogens are positioned across from each other rather than side by side.

Small amounts of trans fats occur naturally in dairy and other animal foods. However, nothing is natural about the trans fats used in processed foods.

These trans fats are produced by adding hydrogen to unsaturated fats to create a product that functions more like a saturated fat. Ingredient labels often list them as “partially hydrogenated” fats.

Consuming trans fats can lead to a number of health problems. Artificial trans fatsare linked to inflammation, unhealthy cholesterol changes, impaired artery function, insulin resistance and excess belly fat (23, 24, 25, 26, 27, 28).

One study estimated that replacing trans fat with other fats could reduce heart disease risk by up to 40%, depending on the type and amount of fat substituted (29).

Trans fats are often found in margarine and other processed spreads. Food manufacturers sometimes add them to packaged products such as crackers to help extend shelf life.

Bottom Line: Fats are grouped by the number of bonds in their carbon chains. Aside from trans fats, most fats have beneficial or neutral effects on health. However, a high omega-6 to omega-3 ratio may cause problems.

How Much Fat Should You Really Eat Every Day?

Photo: domoyega / Getty Images

Thanks to the sudden popularity of the ketogenic diet, fat has been thrust into the spotlight. Of the three macronutrients (protein, carbs, and fat), it’s fair to say it’s the buzziest at the moment. People are even making “fat bombs” and eating bacon on the reg to increase their daily fat intake in the name of health. Others (maybe those who have watched What the Health?) take the opposite approach and advocate for low-fat, zero-oil, plant-based diets.

But how much fat is it actually healthy to eat, and how low-fat is too low? Here’s everything you need to know, straight from nutrition pros.

What are the different types of fats?

FYI: Not all fats are created equal. (That’s why the term “healthy fats” exists in the first place.) There are four main types of fats:

  • Monounsaturated fats are found in plant foods like nuts, avocado, and olive oil.
  • Polyunsaturated fats are found in nuts, seeds, olive oil, and certain kinds of fish. They also include omega-3 and omega-6 fatty acids.
  • Saturated fats are mostly found in animal products like meat and dairy.
  • Trans fats are mostly man-made and created by a process called hydrogenation that turns liquid fats into solids. This process has been banned in the U.S., since it can raise your LDL (“bad”) cholesterol and lower your HDL (“good”) cholesterol. Small amounts of trans fats also occur naturally in some animal products, like fatty cuts of meat.

Of these four, dietitians recommend focusing on monounsaturated and polyunsaturated fats, eating saturated fats in moderation, and avoiding trans fats entirely.

“Monounsaturated and polyunsaturated fats improve blood cholesterol levels and reduce the risk for heart disease,” explains Kimberly Yawitz, a registered dietitian with McDaniel Nutrition Therapy. “There’s also some evidence that they lower the risk for type 2 diabetes, particularly when they replace refined carbohydrates like sweets, white bread, and fruit juices. Omega-3 fatty acids have also been found to lower blood pressure, decrease blood triglycerides, and prevent fatty plaque from building up in the arteries.”

Here’s how to find the right amount of daily fat intake for you.

With all the high-fat/low-fat aficionados out there, it’s hard to know what’s actually right for you. Here’s what experts suggest for figuring out your own personal ideal level of dietary fat.

Start off with the standard fat recommendation. If you’re not sure what fat intake is right for you, give dietitians’ standard recommended daily intake a try and take it from there. “A good rule of thumb is to aim for 20 to 35 percent of your calories from fat,” says Maryann Walsh, a registered dietitian in Jupiter, FL. “You can multiply this percentage by your daily calorie intake, then divide that number by 9 to get the grams of fat per day.” If math isn’t your thing, apps like MyFitnessPal can help you figure this out, says Walsh.

Think long-term. Sure, that keto diet might sound like a good idea right now, but can you imagine yourself eating that way a year from now? If not, experts recommend picking a fat intake you can stick with. “Think about the healthy foods you love eating on a daily basis,” suggests Yawitz. “If you’re a carb queen, you’d probably do well with a low-fat diet. A good starting point would be about 25 percent of your daily calories from fat. If you enjoy nuts, seeds, avocado, and cheese, you’d likely feel deprived on a lower-fat diet. You’ll probably want to aim for 30 to 35 percent of calories from fat.”

Keep an eye on your numbers. “Once you set a goal for your fat intake, try tracking your meals and snacks for a few days,” says Yawitz. “As you track, pay attention to your hunger and energy levels, as well as your body weight. If your body weight increases more than you’d like, you may need to either lower your fat intake or cut calories from carbs or protein. You may also try adjusting your fat level if you’re at the lower end and frequently find yourself tired or hungry.”

Have some fat with every meal. “The best rule of thumb is to include a plant-based source of unsaturated fat at almost every meal/snack,” says Rachel Fine, a registered dietitian nutritionist at To The Point Nutrition. “Not only does adding fat to a meal improve satiety, but it also helps to maintain blood sugar levels by balancing the carbohydrate in the meal. Overall, meals and snacks should be a balance among the three macronutrients: complex carbs, health unsaturated fats, and lean protein.”

Do you. “At the end of the day, there are a lot of opinions out there, but you need to do what works best for you,” says Walsh.

What’s the deal with high-fat diets?

High-fat diets are surging in popularity right now. But are there any real benefits to eating a higher-fat diet? “High-fat diets have gained a lot of popularity because people often experience weight loss in the first week or two. However, it’s important to keep in mind that when limiting carbohydrates in the diet, you will initially lose water weight, not experience true fat loss, explains Lauren Manganiello, a registered dietitian and certified personal trainer. (People also experience something called keto flu, partially due to the fact that they’re losing more water than normal.)

High-fat, low-carb diets are also not a great idea if you’re super into fitness. “In order for athletes to perform optimally, they need an appropriate balance of carbs, protein, and fat for performance as well as recovery,” says Manganiello. “Typically, I would not recommend a high-fat diet for an athlete.” (FWIW, there are some endurance athletes who swear by a higher-fat diet. Here’s what you need to know about exercising on the keto diet.)

On the plus side: “Many people often claim that they don’t feel as hungry on high-fat diets compared to other diets,” says Manganiello. “This is probably because fat helps contribute to us feeling satiated after a meal.” Still, satiety is subjective, so this isn’t a guarantee.

What about low-fat diets?

The low-fat approach is one nutrition pros are more open to, as long as you’re not going *too* low. “Dietary fat has many important functions in the body,” notes Yawitz. “It helps insulate the body against cold and is important for healthy skin and hair. Unsaturated fats have also been found to promote brain health, reduce inflammation, and ward off depression and other mood disorders. For optimal health, you need at least 20 percent of your calories to come from fat.”

There are some legit benefits to keeping your fat intake in the lower range (20 percent of your daily calories or slightly above), though. “A low-fat diet approach is an effective method of calorie control, as fat has 9 calories per gram versus carbs and protein, which have 4 calories per gram,” explains Walsh. There is also positive research pointing to a plant-based diet as beneficial for preventing cancer and cardiovascular diseases, she says.

“I typically recommend that women with a family history of heart disease or abnormal cardiovascular labs follow a lower-fat diet that includes a variety of plant foods,” says Yawitz. “For these women, 20 to 25 percent of calories from fat is a good starting point. It’s also important to limit saturated fat to less than 7 percent of daily calories.” (Related: Can Saturated Fats Help You Live Longer?)

Remember: When in doubt, listen to your body and practice healthy eating habits that you think you can stick to your whole life, says Walsh. “The best nutrition plan is the one that works for you and incorporates the foods you love.”

More and more food labels are starting to include trans fats. If the amount of trans fats is not included on the label, you can estimate the amount by adding up the total amount of polyunsaturated, monounsaturated and saturated fat. If that’s less than the total fat on the package, the difference is trans fat.

Where Do I Start?

  • Eat a variety of lower-fat foods to get all the nutrients you need.
  • Watch your calorie intake. Remember, “low fat” does not always mean “low calorie.”
  • Eat plenty of plant-based foods (such as grain products, fruits and vegetables) and a moderate amount of animal-based foods (meat and dairy products) to help control your fat, cholesterol and calorie intake.
  • Increase your physical activity to improve heart health and lose excess body fat.

What Goals Should I Try to Meet?

  • Decrease the total amount of fat you eat to 20%-35% or less of your total daily calories. For a person eating 2,000 calories a day, this would be 44-77 grams of fat or less per day.
  • Limit cholesterol intake to 300 milligrams (mg) or less per day.
  • Decrease saturated fat (animal fat, butter, coconut and palm oils) to less than 10% of your total calories per day. For a person eating 2000 calories a day, this would be 22 grams of saturated fat or less per day.

Tips for Reducing Fat Intake

When selecting foods:

  • Learn about the foods you eat by reading nutrition labels. Lookfor “low-fat,” “nonfat” and “reduced-fat” claims on food packages. Focus on total fat, rather than individual items. When selecting food, balance those with a higher fat amount against those with a lower fat amount to stay within your fat total or “budget” for the day.
  • Choose lean meats, fish and poultry. Limit these to 5-7 ounces per day. Other good low-fat sources of protein include dried beans and peas, tofu, low-fat yogurt, low-fat milk, low-fat cottage cheese and tuna fish packed in water. Choose skim or 1% milk.
  • Enjoy low-fat (no more than 3 grams of fat per ounce) or nonfat cheeses and spreads.Try low-fat or fat-free versions of your favorite margarine, salad dressing, cream cheese and mayonnaise.

When preparing foods:

  • Trim all visible fat and remove the skin from poultry.
  • Refrigerate soups, gravies and stews, and remove the hardened fat before eating.
  • Bake, broil or grill meats on a rack that allows fat to drip from the meat. Avoid frying foods.
  • Sprinkle lemon juice and herbs/spices on cooked vegetables instead of using cheese, butter or cream-based sauces.
  • Try plain, nonfat or low-fat yogurt and chives on baked potatoes rather than sour cream. Reduced-fat sour cream still contains fat, so you must limit the amount you use.

When dining out:

  • Choose simply-prepared foods such as broiled, roasted or baked fish or chicken. Avoid fried or sauteed foods, casseroles, and foods with heavy sauces and gravies.
  • Request that your food be cooked without added butter, margarine, gravy or sauces.
  • Request salad with low-fat dressing on the side.
  • Select fruit, angel food cake, nonfat frozen yogurt, sherbet or sorbet for dessert instead of ice cream, cake or pie.

Reviewed by the Department of Nutrition Therapy at The Cleveland Clinic.

Edited by Charlotte Grayson, MD, WebMD, August 2004.
Portions of this page © The Cleveland Clinic 2000-2004

QUESTION

According to the USDA, there is no difference between a “portion” and a “serving.” See Answer

The Benefits of a Low-Fat Diet

If you are thinking about losing weight, you might want to consider a low-fat diet. It’s a healthy approach that gives you all the nutritional components you need.

The Low-Fat Diet: Everyone Benefits

“I’m a big advocate of following a low-fat diet as an eating plan for life, rather than a diet that you go on and get off,” says Elizabeth Ricanati, MD, medical director for Lifestyle 180 at the Wellness Institute, Cleveland Clinic Foundation. “If you want good health, you need to eat a healthy diet. You don’t put tomato juice in a car and expect it to work.”

In addition to helping you lose weight by using calories on more filling foods, following a low-fat diet can help you ward off serious medical conditions, including heart disease, high cholesterol, and diabetes.

The Low-Fat Diet: Choose Wisely

The body needs some fat to function properly. But even though every gram of fat contains 9 calories, not all fats stack up the same nutritionally. Some are better for you than others:

  • Unsaturated fats include both monounsaturated and polyunsaturated fats, which come from plants; you know them as olive, corn, and canola oils, among others. (Commonly used plant-based foods you want to avoid because they contain saturated fat are coconut, palm oil, and cocoa butter.) On a low-fat diet that limits the amount of fat you can eat, most of your fats should be from this category.
  • Saturated fats come from animal products such as meat and dairy foods. They increase the risk of heart disease because they raise the “bad” LDL cholesterol in the body. According to the National Institutes of Health (NIH), 10 percent or less of your daily calories should be from saturated fats. The American Heart Association recommends even less — 7 percent.
  • Trans fats are found in products like margarines and shortening as well as in many snacks such as cookies, cakes, pies, and potato chips. Trans fats are created when a food manufacturer changes liquid oils into more solid fats, sometimes called “partially hydrogenated oils,” often to increase the shelf life of packaged food. Trans fats can raise your bad cholesterol. Dr. Ricanati recommends avoiding them altogether.

The Low-Fat Diet: Tracking Fat Grams and Calories

To follow a low-fat diet, keep track of how many calories and grams of fat you eat and plan most of your meals around lean protein, vegetables, fruit, and whole grains.

  • Low-fat diet for maintenance. Current nutritional guidelines from the NIH suggest that only 20 to 35 percent of your total daily intake should come from fat. For the average 2,000-calorie-a-day maintenance diet, that means about 400 to 700 calories, or 44 to 77 grams of total fat per day. Want to follow a low-fat diet? Aim for the low end of that range, with most of the fat in your diet coming from unsaturated sources. To keep saturated fat to 10 percent of your total intake, limit it to 200 calories or 22 grams of fat per day, taken from your daily fat allowance.
  • Low-fat diet for weight loss. On a weight-loss diet of 1,200 calories, limiting fats to only 20 percent of total daily intake means you can have 240 calories, or 26 grams, of fat each day, with a maximum of 120 calories, or 13 grams, coming from saturated fat. That leaves you nearly 1,000 calories to “spend” on protein and carbohydrates.

While it’s hard to know exactly how many fat grams are in a piece of red meat (you can estimate using a calorie-counting guidebook), for packaged foods, the nutritional label tells you everything you need to know, including total fat grams and calories, and the grams and calories of any saturated and trans fat in the food.

The Low-Fat Diet: Better Building Blocks

“A low-fat diet includes fruits, vegetables, whole grains, and proteins such as lean meat and fish,” says Tera Fridley, RD, LD, clinical nutrition manager at AVI Foodsystems, Hillcrest Hospital, a Cleveland Clinic hospital in Mayfield Heights, Ohio. How you prepare food is important. Use low-fat methods — baked, roasted, or broiled instead of deep-fried. “You can eat all kinds of delicious foods on a low-fat diet,” Fridley says. “If you have a favorite food that’s high in fat, you can still enjoy it in moderation.”

When calorie counting to lose weight, be sure your calories are spread out wisely:

  • To get enough calcium, don’t shun dairy products — just choose low-fat or fat-free milk, yogurt, and cheese for your needed three servings a day.
  • Eat whole-grain foods like rye or whole-wheat bread, whole-wheat crackers, brown rice, popcorn (without butter!), barley, and bulgur wheat.
  • Get your fill of fresh produce — usually 2 cups of fruits and 2 1/2 cups of vegetables — every day. Have a rainbow of colors to get an assortment of vitamins and minerals.

Ricanati emphasizes that a low-fat diet doesn’t need to focus on what you’re skipping: “If you’re trying all the new, wonderful things you can have on a low-fat diet, you’re unlikely to feel deprived.”

Results from large, long Women’s Health Initiative Dietary Modification Trial shows no effect on heart disease, breast cancer, colorectal cancer, or weight.

The low-fat, high-starch diet that was the focus of dietary advice during the 1990s-as reflected by the USDA food guide pyramid-is dying out. A growing body of evidence has been pointing to its inadequacy for weight loss or prevention of heart disease and several cancers. The final nail in the coffin comes from an eight-year trial that included almost 49,000 women. Although the media have made much of the “disappointing” results from the Women’s Health Initiative (WHI) Dietary Modification Trial, it would be a serious mistake to use these new findings as reason to load up on sausage, butter, and deep-fried fast food.

The trial and its findings

The Women’s Health Initiative Dietary Modification Trial was started back in 1993, at a time when dietary fat was seen as a dietary evil and the low-fat diet was thought to be a straightforward route to preventing heart disease, some cancers, and the epidemic of obesity that was beginning to sweep the country. With funding from the National Heart, Lung, and Blood Institute, researchers recruited almost 50,000 women between the ages of 50 and 79 years. Of these, 19,541 were randomly assigned to follow a low-fat diet. Their goal was to lower their fat intake from almost 38% of calories to 20%. They were helped in this effort by a series of individual and group counseling sessions.Another 29,294 women were randomly assigned to continue their usual diets, and were given just generic diet-related educational materials.

After eight years, the researchers looked at how many (and what percentage) of women in each group had developed breast cancer or colorectal cancer. They tallied up heart attacks, strokes, and other forms of heart disease. They also looked at things like weight gain or loss, cholesterol levels, and other measures of health.

The results, published in the Journal of the American Medical Association, showed no benefits for a low-fat diet. Women assigned to this eating strategy did not appear to gain protection against breast cancer,(1) colorectal cancer,(2) or cardiovascular disease.(3) And after eight years, their weights were generally the same as those of women following their usual diets.(4)

The researchers saw a trend toward a lower risk of breast cancer among women in the low-fat group. This trend was not statistically significant, meaning it could have been due to chance. It could also have been due to the very small weight loss during the early years of the study among women in the low-fat group, who received intensive dietary counseling. There is strong evidence from many studies that being overweight increases the risk of breast cancer after menopause, and that staying slim after menopause is an effective way to reduce risk of breast cancer, along with many other diseases.

Limitations of the study

Some nutrition experts say that the WHI Dietary Modification Trial doesn’t really lay to rest the low-fat hypothesis because the women in the study only modestly lowered their fat, from 38% to 29%. Had they reached the trial’s target of 20%, benefits from the low-fat approach may have become more apparent, these nutritionists suggest.

It is possible that the participants in the low-fat group may have actually overstated how much they reduced their fat intake. This has happened in other studies, as shown by comparisons between self-reported changes and biochemical measures of dietary change. Significant reductions in fat intake are usually reflected in a decrease in HDL (good) cholesterol and an increase in triglycerides. Yet in the WHI trial, there were no differences in blood levels of HDL cholesterol or triglycerides between the low-fat and usual diet groups. This casts doubt on the degree of fat reduction achieved in this study.

Two other limitations of the trial are the study population and duration. The trial included women who were aged 50 to 79 years at the beginning of the trial. By this time in life, it may be too late for changes in diet to reduce risks of cancer and other chronic conditions. In addition, it takes years for the effects of dietary change to be seen, and so it is possible that eight years wasn’t enough time to see the true impact of a low-fat diet.

The debate will likely continue as to why the WHI observed little benefit for a low-fat diet. Was it because reducing the intake of dietary fat truly has little benefit? Was it because the women in the trial didn’t lower fat intake enough? Or had the study focused on a younger population, or lasted longer, would it have revealed a benefit?

In any case, the dietary intervention didn’t work, even though the WHI trial was, by far, the most expensive study of diet ever conducted (costing many hundreds of millions of dollars) and even though the women in the low-fat group received intensive dietary counseling from some of the best nutritionists and dietitians in the country.

Change was already in the air

The dietary fat reduction arm of the WHI (it also has a hormone replacement therapy component and a calcium and vitamin D component) was controversial from the beginning.(5-8) Members of the HSPH Department of Nutrition argued that the hypothesis that a reduction in total fat intake would have major health benefits was not supported by existing data. It also noted that maintaining a contrast in diets between two groups over many years was difficult, and for this reason the study might not provide a clear answer even if the hypothesized benefits were true.

Such a study had failed in the past. The Multiple Risk Factors Intervention Trial (MRFIT, often called Mister Fit) aimed to decrease risk of coronary heart disease by a program aimed at controlling key risk factors for the disease. Some of the participants received intensive counseling to stop smoking, control high blood pressure, and reduce their intake of saturated fat. At the end of the trial, there was no significant difference in rates of coronary heart disease.(9) Even so, the investigators argued that their hypotheses were still correct because the members of the control group had, on their own, began to stop smoking and eat less saturated fat, making differences in smoking rates and diet between the two randomized groups very small.(10) The results of the WHI add further evidence that clear answers to questions about the long term effects of diet on risks of cancers and other major diseases may not be obtainable by large randomized intervention trials, no matter how much money is spent conducting them.

Type trumps percentage

The findings from the Women’s Health Initiative Dietary Modification Trial came as a surprise to many Americans who have been hearing for years that reducing fat is important for long-term health. Yet long-term follow-up studies such as the Nurses Health Study have consistently found little relation between the percentage of calories from fat and risks of breast cancer, colon cancer, or coronary heart disease. Such studies are one reason why major reviews of diet and health during the last five years, including those conducted by the U.S. Institute of Medicine and the U.S. Dietary Guidelines Committee, have moved away from advocating low fat intake to an emphasis on the type of fat.

Many lines of evidence indicate that the type of fat is very important to long-term health. Replacing saturated and trans with natural vegetable oils can greatly reduce the risk of heart disease and diabetes. In the Nurses’ Health Study II we have seen that women who consume high amounts of red meat and high-fat dairy foods during their early adult years are at increased risk of developing breast cancer.

Making good dietary choices does really matter, but it is the type of fat, not the amount, that is most important. And keep in mind that too many calories from both fat and carbohydrate will lead to weight gain, which will increase risks of breast cancer, colon cancer, and heart disease.

1. Prentice RL, Caan B, Chlebowski RT, et al. Low-fat dietary pattern and risk of invasive breast cancer: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA. 2006; 295:629-42.
2. Beresford SA, Johnson KC, Ritenbaugh C, et al. Low-fat dietary pattern and risk of colorectal cancer: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA.2006; 295:643-54.
3. Howard BV, Van Horn L, Hsia J, et al. Low-fat dietary pattern and risk of cardiovascular disease: the Women’s Health Initiative Randomized Controlled Dietary Modification Trial. JAMA. 2006; 295:655-66.
4. Howard BV, Manson JE, Stefanick ML, et al. Low-fat dietary pattern and weight change over 7 years: the Women’s Health Initiative Dietary Modification Trial. JAMA. 2006; 295:39-49.
5. Michels KB, Willett WC. The women’s health initiative: will it resolve the issues? Recent Results in Cancer Research. 1996; 140:295-305.
6. Prentice RL, Sheppard L. Dietary fat and cancer: consistency of the epidemiologic data, and disease prevention that may follow from a practical reduction in fat consumption. Cancer Causes and Control. 1990; 1:81-97; discussion 99-109.
7. Prentice RL, Sheppard L. Dietary fat and cancer: rejoinder and discussion of research strategies. Cancer Causes and Control. 1991; 2:53-8.
8. Willett WC, Stampfer MJ. Dietary fat and cancer: another view? Cancer Causes and Control. 1990; 1:103-109.
9. Multiple risk factor intervention trial. Risk factor changes and mortality results. Multiple Risk Factor Intervention Trial Research Group. JAMA. 1982; 248:1465-77.
10. Willett W. Nutritional epidemiology. New York: Oxford University Press, 1998.

A low-fat diet was strongly advocated in the late 1970s as a healthier alternative to the mainstream, high-fat American diet of the 1960s. Given the association of high fat with additional calories and the harms of increased saturated fat intake, this recommendation from both the federal government and professional organizations had some logic. Unfortunately, this dietary advice backfired dramatically. Without detailed, clear instructions about what to eat in place of fats, a low-fat diet was often dominated by unhealthy, processed carbs.

Health rationale slogan: By restricting fat, you can stay thin and avoid heart disease and cancer.

Analysis: A diet that greatly reduces fat can be a good diet, but only if fibrous vegetables, fruits, beans/legumes, and whole grains replace the missing fat. When fat intake is, instead, shifted to bread, desserts, and breakfast cereal, the results can be disastrous.

“Recommending a low-fat diet backfired when the food industry realized that lower fat content of many products also lowered palatability and sales, which they typically addressed by adding sugars and refined grains. These new, low-fat products were marketed as healthier choices — which they were not,” said Stanford nutrition scientist Christopher Gardner, PhD.

As we now know, not all fats are bad. There is a distinction between good fats (unsaturated fats from nuts, vegetable oils and fish) and bad fats (saturated or trans fat from red meat, dairy and processed foods). While many consider the low-fat diet to be discredited, if it is modified to avoid processed carbs and to include healthier forms of fat, this diet can be a healthy pattern of eating.

Easy to follow?: Relatively easy to follow at home, but sometime more difficult in eating out because some restaurants have limited low-fat selections.

Dominant source of protein: Lean meats, non-fat dairy products, legumes (including soy products), nuts, grains.

Most common fats: Plant-based are a better choice.

What about carbs?: Open season on carbs, at least in the older version of this diet.

When it goes wrong: For the average American, fat-containing meat is a dominant part of many meals. Substituting highly processed foods where sugars and refined flour dominate can create an unhealthy low-fat diet.

To make it healthier: A lower fat diet emphasizing fibrous vegetables, beans/legumes, fruits, and whole grains facilitates health. A low-fat pattern of eating will remain a healthy diet as long as highly processed foods are minimized.

Variations: A low-fat diet should ideally be a low saturated fat diet. A Mediterranean diet and many vegetarian diets approximate this goal of low saturated fat intake and are very healthy lower fat diets.

If you’re going to cheat: Liberalizing the intake of fats from fish and plants can lead to a more satisfying and easier to follow pattern of eating.

Conclusion: A lower fat diet can be a disaster if fats are replaced by high glycemic index carbohydrates, those simple carbs like sugar and flour that are digested very quickly. However, a lower fat diet can be a good choice given the benefits of many plant-based foods, but only if it incorporates the whole grains, fruits, beans/legumes and fibrous vegetables that are a natural part of many of the other diets discussed in this blog series. The past experience with low-fat diets is a prime example of unintended consequences when dietary advice is not clear and detailed.

This is the eighth post in a series called A Skeptical Look at Popular Diets. The series reviews the eight currently most prominent diets in America. The next, final blog post will discuss a Mediterranean diet.

Randall Stafford, MD, PhD, is a professor of medicine at Stanford. He practices primary care internal medicine and studies strategies for preventing chronic disease. Stanford professor and nutrition scientist Christopher Gardner, PhD, examines the impact of diet on health and disease. Min Joo Kim provided research assistance.

Photo by TiBine

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