Why are carbohydrates important

Balancing carbs, protein, and fat

Three nutrients — carbohydrate, protein, and fat — contain calories that your body uses for energy. Here’s how to balance these nutrients in a healthy diet.

Carbohydrate has 4 calories per gram. About 50 to 60 percent of your total daily calories should come from carbohydrate.

Carbohydrate contains the most glucose and gives the quickest form of energy. Your body changes 100 percent of carbohydrate into glucose.

Besides giving your body energy that it uses right away, your body can store carbohydrate in your liver. Your liver stores extra carbohydrate as glycogen and releases it later, when your body needs it. However, there’s a limit to the amount of glycogen your liver can store. Once your liver has reached that limit, your body turns the extra carbohydrate into fat.

There are two types of carbohydrate: healthy and not-so-healthy.

Healthy carbs: Also called complex or slower-acting carbs. Includes multigrain bread, brown rice, lentils, and beans. This type of carbohydrate raises blood sugar slowly and lasts longer. This helps keep you from feeling hungry for a longer time and helps to keep blood sugar levels closer to normal.

Not-so-healthy carbs: Also known as simple or fast-acting carbs. Includes candy, cookies, cake, soda, juice, and sweetened beverages. This type of carbohydrate raises blood sugar levels very quickly, but doesn’t last very long. That’s why these carbs work well to correct low-blood sugar but don’t satisfy hunger as well as healthy carbs.

Protein also has 4 calories per gram. In a healthy diet, about 12 to 20 percent of your total daily calories should come from protein.

Your body needs protein for growth, maintenance, and energy. Protein can also be stored and is used mostly by your muscles. Your body changes about 60 percent of protein into glucose.

Protein takes 3 to 4 hours to affect blood sugar levels. When it does have an effect, foods that are mostly protein won’t cause much of a rise in blood sugar.

Fat has the most calories of all the nutrients: 9 calories per gram. In a healthy diet, about 30 percent of total daily calories should come from fat. This means eating about 50 to 80 grams of fat each day. Fat gives the body energy, too, but the body changes only about 10 percent of fat into glucose.

By itself, fat doesn’t have much impact on blood sugar. But when you eat fat along with a carbohydrate, it can slow the rise in blood sugar. Since fat also slows down digestion, once your blood sugar does rise, it can keep your blood sugar levels higher for a longer period of time.

There are various types of fat, and some types are better for you than others. Choose mono-unsaturated or poly-unsaturated fat. These fats are liquid at room temperature. Mono-unsaturated fats are especially healthy because they lower the bad cholesterol (LDL) in your blood. These fats include olive, canola, avocado, and nut oils.

Limit saturated and trans-fats. Saturated fats are found in foods that come from animals, such as meat and dairy products. These kinds of fats are solid at room temperature. Hardened fats, such as coconut or palm kernel oils as well as oils that have been hydrogenated, also contain saturated fat. These can damage your heart and arteries.

Trans-fats are found in most processed foods and many fried fast foods, such as French fries. They help food stay fresher longer, but they’re just as bad for you as saturated fat.

Clinical review by Meredith Cotton, RN
Kaiser Permanente
Reviewed 01/03/2019

Chapter 7 Carbohydrates

Carbohydrates are part of a healthful diet. The AMDR for carbohydrates is 45 to 65 percent of total calories. Dietary fiber is composed of nondigestible carbohydrates and lignin intrinsic and intact in plants. Diets rich in dietary fiber have been shown to have a number of beneficial effects, including decreased risk of coronary heart disease and improvement in laxation. There is also interest in the potential relationship between diets containing fiber-rich foods and lower risk of type 2 diabetes. Sugars and starches supply energy to the body in the form of glucose, which is the only energy source for red blood cells and is the preferred energy source for the brain, central nervous system, placenta, and fetus. Sugars can be naturally present in foods (such as the fructose in fruit or the lactose in milk) or added to the food. Added sugars, also known as caloric sweeteners, are sugars and syrups that are added to foods at the table or during processing or preparation (such as high fructose corn syrup in sweetened beverages and baked products). Although the body’s response to sugars does not depend on whether they are naturally present in a food or added to the food, added sugars supply calories but few or no nutrients.

Consequently, it is important to choose carbohydrates wisely. Foods in the basic food groups that provide carbohydrates—fruits, vegetables, grains, and milk—are important sources of many nutrients. Choosing plenty of these foods, within the context of a calorie-controlled diet, can promote health and reduce chronic disease risk. However, the greater the consumption of foods containing large amounts of added sugars, the more difficult it is to consume enough nutrients without gaining weight. Consumption of added sugars provides calories while providing little, if any, of the essential nutrients.


  • Choose fiber-rich fruits, vegetables, and whole grains often.
  • Choose and prepare foods and beverages with little added sugars or caloric sweeteners, such as amounts suggested by the USDA Food Guide and the DASH Eating Plan.
  • Reduce the incidence of dental caries by practicing good oral hygiene and consuming sugar- and starch-containing foods and beverages less frequently.


The recommended dietary fiber intake is 14 grams per 1,000 calories consumed. Initially, some Americans will find it challenging to achieve this level of intake. However, making fiber-rich food choices more often will move people toward this goal and is likely to confer significant health benefits.

The majority of servings from the fruit group should come from whole fruit (fresh, frozen, canned, dried) rather than juice. Increasing the proportion of fruit that is eaten in the form of whole fruit rather than juice is desirable to increase fiber intake. However, inclusion of some juice, such as orange juice, can help meet recommended levels of potassium intake. Appendixes B-1 and B-8 list some of the best sources of potassium and dietary fiber, respectively.

Legumes—such as dry beans and peas—are especially rich in fiber and should be consumed several times per week. They are considered part of both the vegetable group and the meat and beans group as they contain nutrients found in each of these food groups.

Consuming at least half the recommended grain servings as whole grains is important, for all ages, at each calorie level, to meet the fiber recommendation. Consuming at least 3 ounce-equivalents of whole grains per day can reduce the risk of coronary heart disease, may help with weight maintenance, and may lower risk for other chronic diseases. Thus, at lower calorie levels, adults should consume more than half (specifically, at least 3 ounce-equivalents) of whole grains per day, by substituting whole grains for refined grains. (See table 7 for a list of whole grains available in the United States.)

Individuals who consume food or beverages high in added sugars tend to consume more calories than those who consume food or beverages low in added sugars; they also tend to consume lower amounts of micronutrients. Although more research is needed, available prospective studies show a positive association between the consumption of calorically sweetened beverages and weight gain. For this reason, decreased intake of such foods, especially beverages with caloric sweeteners, is recommended to reduce calorie intake and help achieve recommended nutrient intakes and weight control.

Total discretionary calories should not exceed the allowance for any given calorie level, as shown in the USDA Food Guide (see ch. 2). The discretionary calorie allowance covers all calories from added sugars, alcohol, and the additional fat found in even moderate fat choices from the milk and meat group. For example, the 2,000-calorie pattern includes only about 267 discretionary calories. At 29 percent of calories from total fat (including 18 g of solid fat), if no alcohol is consumed, then only 8 teaspoons (32 g) of added sugars can be afforded. This is less than the amount in a typical 12-ounce calorically sweetened soft drink. If fat is decreased to 22 percent of calories, then 18 teaspoons (72 g) of added sugars is allowed. If fat is increased to 35 percent of calories, then no allowance remains for added sugars, even if alcohol is not consumed.

In some cases, small amounts of sugars added to nutrient-dense foods, such as breakfast cereals and reduced-fat milk products, may increase a person’s intake of such foods by enhancing the palatability of these products, thus improving nutrient intake without contributing excessive calories. The major sources of added sugars are listed in table 13 (app. A-3 provides examples of how added sugars can fit into the discretionary calorie allowance).

The Nutrition Facts Panel on the food label provides the amount of total sugars but does not list added sugars separately. People should examine the ingredient list to find out whether a food contains added sugars. The ingredient list is usually located under the Nutrition Facts Panel or on the side of a food label. Ingredients are listed in order of predominance, by weight; that is, the ingredient with the greatest contribution to the product weight is listed first and the ingredient contributing the least amount is listed last. Table 14 lists ingredients that are included in the term “added sugars.” 14

Sugars and starches contribute to dental caries by providing substrate for bacterial fermentation in the mouth. Thus, the frequency and duration of consumption of starches and sugars can be important factors because they increase exposure to cariogenic substrates. Drinking fluoridated water and/or using fluoride-containing dental hygiene products help reduce the risk of dental caries. Most bottled water is not fluoridated. With the increase in consumption of bottled water, there is concern that Americans may not be getting enough fluoride for maintenance of oral health. A combined approach of reducing the frequency and duration of exposure to fermentable carbohydrate intake and optimizing oral hygiene practices, such as drinking fluoridated water and brushing and flossing teeth, is the most effective way to reduce incidence of dental caries.

Considerations for Specific Population Groups

Older Adults

Dietary fiber is important for laxation. Since constipation may affect up to 20 percent of people over 65 years of age, older adults should choose to consume foods rich in dietary fiber. Other causes of constipation among this age group may include drug interactions with laxation and lack of appropriate hydration (see ch. 2).


Carbohydrate intakes of children need special considerations with regard to obtaining sufficient amounts of fiber, avoiding excessive amounts of calories from added sugars, and preventing dental caries. Several cross-sectional surveys on U.S. children and adolescents have found inadequate dietary fiber intakes, which could be improved by increasing consumption of whole fruits, vegetables, and whole-grain products. Sugars can improve the palatability of foods and beverages that otherwise might not be consumed. This may explain why the consumption of sweetened dairy foods and beverages and presweetened cereals is positively associated with childrens’ and adolescents’ nutrient intake. However, beverages with caloric sweeteners, sugars and sweets, and other sweetened foods that provide little or no nutrients are negatively associated with diet quality and can contribute to excessive energy intakes, affirming the importance of reducing added sugar intake substantially from current levels. Most of the studies of preschool children suggest a positive association between sucrose consumption and dental caries, though other factors (particularly infrequent brushing or not using fluoridated toothpaste) are more predictive of caries outcome than is sugar consumption.

TABLE 13. Major Sources of Added Sugars (Caloric Sweeteners) in the American Diet Food Categories Contribution to Added Sugars Intake

Food groups that contribute more than 5 percent of the added sugars to the American diet in decreasing order.

Food Categories Contribution to Added Sugars Intake
(percent of total added sugars consumed)
Regular soft drinks 33.0
Sugars and candy 16.1
Cakes, cookies, pies 12.9
Fruit drinks (fruitades and fruit punch) 9.7
Dairy desserts and milk products
(ice cream, sweetened yogurt, and sweetened milk)
Other grains (cinnamon toast and honey-nut waffles) 5.8

Source: Guthrie and Morton, Journal of the American Dietetic Association, 2000.

TABLE 14. Names for Added Sugars That Appear on Food Labels

Some of the names for added sugars that may be in processed foods and listed on the label ingredients list.

Brown sugar Invert sugar
Corn sweetener Lactose
Corn syrup Maltose
Dextrose Malt syrup
Fructose Molasses
Fruit juice concentrates Raw sugar
Glucose Sucrose
High-fructose corn syrup Sugar
Honey Syrup

14 For information on amounts of added sugars in some common foods, see Krebs-Smith, SM. Choose beverages and foods to moderate your intake of sugars: measurement requires quantification. The Journal of Nutrition (J Nutr) 131(2S-I): 527S-535S, 2001.

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Updated Wednesday, July 09, 2008 by ODPHP Web Support

Carbohydrates and Sugar

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What Are Carbohydrates?

Carbohydrates are the body’s most important and readily available source of energy. They’re a necessary part of a healthy diet for both kids and adults.

The two main forms of carbs are:

  1. simple carbohydrates (or simple sugars): including fructose, glucose, and lactose, which also are found in nutritious whole fruits
  2. complex carbohydrates (or starches): found in foods such as starchy vegetables, whole grains, rice, and breads and cereals

So how does the body process carbs and sugar? All carbohydrates are broken down into simple sugars, which are absorbed into the bloodstream. As the sugar level rises, the pancreas releases the hormone insulin, which is needed to move sugar from the blood into the cells, where the sugar can be used as energy

The carbs in some foods (mostly those that contain simple sugars and highly refined grains, such as white flour and white rice) are easily broken down and cause blood sugar levels to rise quickly.

Complex carbs (found in whole grains), on the other hand, are broken down more slowly, allowing blood sugar to rise gradually. A diet that’s high in foods that cause a rapid rise in blood sugar may increase a person’s risk of developing health problems like diabetes.

Some carbohydrate-dense foods are healthier than others. Good options include:

  • whole-grain cereals
  • brown rice
  • whole-grain breads
  • fruits
  • vegetables
  • low-fat dairy

A healthy balanced diet for kids over 2 years old should include 50% to 60% of calories coming from carbohydrates. The key is to make sure that the majority of these carbs come from good sources and that added sugar is limited.

Are Some Carbs Bad?

Carbohydrates have taken a lot of heat in recent years. Medical experts think eating too many refined carbs — such as the refined sugars in candy and soda, and refined grains like the white rice and white flour used in many pastas and breads — have contributed to the rise of obesity in the United States.

How could one type of food cause such a big problem? The “bad” carbs (sugar and refined foods) are easy to get, come in large portions, taste good, and aren’t too filling. So people tend to eat more of them than needed. And some are not needed at all — sodas and candy are “empty calories” that provide no nutrients.

But this doesn’t mean that all simple sugars are bad. Simple carbs are also found in many nutritious foods — like fruits, vegetables, and dairy products, which provide a range of essential nutrients that support growth and overall health. Fresh fruits, for example, contain simple carbs but also have vitamins and fiber.

Why Are Complex Carbs Healthy?

The 2015–2020 Dietary Guidelines for Americans recommend eating grains, at least half of which should be complex carbs. Whole grains, like brown rice, oatmeal, and whole-grain breads and cereals, are the way to go. Diets rich in whole grains protect against diabetes and heart disease. And complex carbs:

  • Break down more slowly in the body: Whole grains contain all three parts of the grain (the bran, germ, and endosperm), whereas refined grains are mainly just the endosperm. Whole grains give your body more to break down, so digestion is slower. When carbs enter the body more slowly, it’s easier for your body to regulate them.
  • Are high in fiber: High-fiber foods are filling and, therefore, discourage overeating. Plus, when combined with plenty of fluid, they help move food through the digestive system to prevent constipation and may protect against gut cancers.
  • Provide vitamins and minerals: Whole grains contain important vitamins and minerals, such as B vitamins, magnesium, and iron.

Most school-age kids should eat four to six “ounce equivalents” from the grain group each day, at least half of which should come from whole grains. An “ounce equivalent” is like a serving — 1 slice of bread; 1 cup of ready-to-eat cereal; or a half cup of cooked rice, cooked pasta, or hot cereal.

What About Sugar?

Foods that are high in added sugar (soda, cookies, cake, candy, frozen desserts, and some fruit drinks) also tend to be high in calories and low in nutrition. A high-sugar diet is often linked with obesity, and too many sugary foods can lead to tooth decay. The 2015–2020 Dietary Guidelines recommend that added sugar be less than 10% of total calories consumed.

Instead of sugary options, offer healthier choices, such as fruit — a naturally sweet carbohydrate-containing snack that also provides fiber and vitamins that kids need.

One way to cut down on added sugar is to ban soda and other sugar-sweetened beverages. Consider these facts:

  • Each 12-ounce (355-ml) serving of a carbonated, sweetened soft drink has the equivalent of 10 teaspoons (49 ml) of sugar and 150 calories. Sweetened drinks are the largest source of added sugar in the daily diets of U.S. children.
  • Drinking one 12-ounce (355-ml) sweetened soft drink per day increases a child’s risk of obesity.
  • Acidity from sweetened drinks can erode tooth enamel and their high sugar content can cause dental cavities.

Instead of soda or juice drinks (which often have as much added sugar as soft drinks), serve low-fat milk, water, or 100% fruit juice. Note: Although there’s no added sugar in 100% fruit juice, the calories from those natural sugars can add up. So limit juice to 4–6 ounces (118–177 ml) for kids under 7 years old, and to no more than 8–12 ounces (237–355 ml) for older kids and teens.

How Can I Find Healthy Options?

It isn’t always easy to tell which foods are good choices and which aren’t. The Nutrition Facts on food labels can help.

To figure out carbohydrates, look for these three numbers:

  1. Total Carbohydrate: This number, listed in grams, combines several types of carbohydrates: dietary fibers, sugars, and other carbs.
  2. Dietary Fiber: Listed under Total Carbohydrate, dietary fiber itself has no calories and a high-fiber diet has many health benefits.
  3. Sugars: Also listed under Total Carbohydrate. The Nutrition Facts label soon will make the distinction between natural sugars and added sugars. Natural sugars are found in such foods as fruit and dairy products. Snack foods, candy, and soda often have lots of added sugars. To see if a food has added sugar, check the ingredients list for sugar, corn syrup, or other sweeteners, such as dextrose, fructose, honey, or molasses, to name just a few. Avoid products that have sugar or other sweeteners high on the ingredients list.

Although carbohydrates have just 4 calories per gram, the high sugar content in snack foods means the calories can add up quickly, and these “empty calories” usually have few other nutrients.

How Can I Make Carbs Part of a Healthy Diet?

Make good carbohydrate choices (buy whole grains, fruits, veggies, and low-fat milk and dairy products), limit foods with added sugar, and encourage kids to be active every day.

And don’t forget to be a good role model. Kids will see your healthy habits and adopt them, leading to a healthier lifestyle in childhood and beyond.

Reviewed by: Jane M. Benton, MD, MPH Date reviewed: January 2017

Why Carbohydrates Are Important for Your Diet

If you choose a low-carbohydrate diet for weight loss and take in fewer calories, you will lose weight. Generally these diets involve eating less bread and pasta and more vegetables, fruits, and meat. Although low-carbohydrate diets work well early on, after six months they do not work any better than any other diets for weight loss.

“If you stop eating carbohydrates, you rapidly lose water weight as your body breaks down the stored carbohydrates,” explains Darwin Deen, MD, senior attending physician at Montefiore Medical Center’s Department of Family and Social Medicine in the Bronx, New York. “The problem is that a low-carbohydrate diet is not a normal balance of physiologic nutrition. As soon as you start eating carbohydrates again, your body replenishes your carbohydrate stores and your weight comes back,” says Dr. Deen.

Eat the Right Carbohydrates for Weight Loss

“Eat plenty of fresh fruits and vegetables, which can add variety, color, and flavor to meals. Whole grains such as whole wheat, corn tortillas, and brown rice are great sources of healthy carbohydrates. Check the nutritional label for carbohydrate information, including total carbohydrates, dietary fiber, and sugars,” says Logan.

Here are ideas for getting the right carbs in your diet: Start your day with a breakfast of whole-grain cereal and fruit. Add an extra serving of vegetables to lunch and dinner. For easy between-meal snacks right at your fingertips, keep raw, cut-up vegetables in the refrigerator. Substitute beans as a main course in place of meat once every week. Eat a whole fruit as your dessert.

Get Your Personal Carbohydrate Guidelines

U.S. guidelines suggest that between 45 and 65 percent of your calories come from carbohydrates. At the USDA Web site, you can enter your age, sex, height, weight, and activity level to find out exactly how many calories in your diet should be from carbohydrates. You will also find the “Easy Fiber Estimator,” which will tell you how many grams of fiber ought to be in every 1,000 calories you eat. For example, if you are on a diet of 2,000 calories, you will want to get 28 grams of dietary fiber.

Concentrate on Calories and Nutrition

The USDA’s Dietary Guidelines for Americans 2005 recommends a balanced eating pattern. If you need to lose weight, you should decrease your calories gradually and increase your physical activity. Choose fiber-rich carbohydrate foods and avoid added sugars. Making healthy carbohydrate choices while reducing calories and increasing physical activity is the healthiest path to weight loss.

Americans certainly have a love-hate relationship when it comes to carbs. European and Asian cultures steadfastly make room for pasta, bread, and rice on their plates, but here in the States, carbs are like fanny-packs: in one day, out the next (and then, back in again?). With the low-carb, high-fat ketogenic diet dominating as the eating plan of the moment, the current consensus seems to be that carbs are no good.

Keto devotees limit their carb intake to just 5 to 10 percent of their diet—vastly lower than the Dietary Guidelines for Americans recommendation that 45 to 65 percent of overall calories come from the macronutrient. The discrepancy between the recs is so big, it feels like both can’t be healthy. So, what’s the deal? Are carbs a vital part of your diet or not?

First, it’s important to know the difference between the various types of carbohydrates out there. “Simple carbs are found in foods like sugary soda and bread, which get absorbed in the body quickly,” explains Wahida Karmally, PH, RDN,CDE, a doctor of public health and special research scientist at Columbia University. “But foods such as vegetables, fruits, nuts, and whole grains have complex carbs, which are full of more nutritional benefits and get absorbed slower.” So when experts talk about carbs being “bad,” it’s mainly the first category they’re discouraging—there is merit to consuming the second category of carbohydrates (more on that in a sec).

Functional medicine practitioner Anthony Gustin, DC, is such a big believer in a low-carb diet that he founded a whole keto company, Perfect Keto. As you might guess, he’s of the mind that you can totally live without carbs—of all types. “Carbohydrates are not important at all,” he says bluntly, saying that while the body can put them to good use, it’s possible to survive without consuming anything at all. “They can be used for energy, but they don’t have to be used for energy.”

Photo: Stocksy/Vera Lair

Gustin explains that when you do eat carbs, the body breaks then down and converts the components to glucose, which then goes into the bloodstream. “Then it’s used for maintenance of red blood cells, brain function, and bodily functions.” Sounds pretty important, right? But while Gustin says blood glucose is indeed vital for fueling the body, breaking down carbohydrates isn’t the only way to make it.

He explains that during a process called gluconeogenesis, non-carbohydrate compounds, like amino acids from protein, are converted to glucose for energy. The body can also use ketones, chemicals created from fat, for energy instead of glucose. (This is, essentially, the whole reasoning behind the keto diet: Without carbs to use for energy, your body will begin to break down fat instead.)

While your body may be able to find other sources of energy, Dr. Karmally warns against cutting carbs out completely—specifically the complex carbs found in healthy foods like fruits and vegetables. “If you do, you’ll be missing out on a whole host of vitamins and nutrients, including fiber, which helps with digestion. That’s why people who go low-carb and increase their fat and protein intake but not their vegetable intake can end up feeling constipated,” she says. To this point, Dr. Karmally says the body can subsist without carbs—it won’t just suddenly shut down on you—but it certainly won’t be in top form: Missing out on the nutrients in fruits and vegetables could lead to more inflammation.

Board-certified sports nutritionist, registered dietitian, and the nutrition director at Trifecta Nutrition Emmie Satrazemis agrees with Gustin that carbs aren’t technically necessary, but like Dr. Karmally, she warns against cutting them out completely. “Even though they aren’t essential for survival, they’re in the majority of foods we eat, including fruits, vegetables, nuts, and seeds. So cutting them out completely would mean missing out on so much nutrition,” she explains, echoing Dr. Karmally’s sentiments.

Satrazemis says there isn’t a hard and fast rule on how many carbs is optimal, but she emphasizes that there’s no need to be scared of carbs or worry they’ll lead to weight gain. “Carbs get a bad rap, but when it comes to maintaining a healthy weight, it’s more about calories,” she says. “If you’re not eating more calories than you need, then you aren’t going to gain weight—even if your diet includes a sizable percentage of carbs.”

Photo: Stocksy/Darren Muir

What about athletes? Don’t they need carbs? Both Gustin and Satrazemis work with professional athletes and have come to the same conclusion: It depends on the type of sport you do. “If you’re doing something that requires short bursts of energy like sprinting or weight lifting, carbs are a better energy source than protein or fats because they’re stored right in the muscles and are more readily available,” Satrazemis says. “But if you’re doing a more sustained workout, like a long run, healthy fat is an ideal energy source because it’s more low-burning.”

“Carbs get a bad rap, but when it comes to maintaining a healthy weight, it’s more about calories.” —Emmie Satrazemis, RD, CSSD

But both experts point out that, alas, the average person doesn’t have the same nutritional needs as a professional athlete and most people overestimate their fueling needs. But, hey, if you keep hitting a wall during your workouts, you could try adding carbs to your pre-workout snack and see if it makes a difference.

The bottom line is that you aren’t going to feel great if you cut complex carbs out completely—even if you could technically survive. According to Dr. Karmally, “People need to focus less on specific nutrients and more on eating whole, real foods because they are going to get more nutritional benefits that way.”

One major dietary point all three experts agree on: Eating unprocessed, real foods should be the goal no matter what. As Gustin aptly puts it, “It doesn’t matter if your diet is low-carb or high-carb, whatever it is, the key should be eating a 100 percent real food, whole foods diet.”

If you’re trying to figure out which healthy eating plan is best for you, check out this guide. Plus, what you need to know about carb backloading.

Can You Survive Without Carbs? | Ask The Dietitian

Are you carb-curious? The popularity of low-carb, ketogenic and other Atkins-style diets are fueling an intense fascination around this macronutrient. As a dietitian and self-professed science junkie, I feel the need to deepen our understanding of this topic so as to not glorify or demonize a nutrient (unless it’s well-deserved!). So, why are carbohydrates so important? Are they really essential in the diet? Read on to find out.


Carbohydrates achieve staple status in our diet because they supply a magical thing called glucose, a sugar. (OK, it’s not magic, just science.) If you weren’t automatically transported back to biology, let me explain.


Our body runs on calories, and it gets those calories by metabolizing carbohydrates, fat and protein from our food. Since our body smartly spares protein for rebuilding and repairing tissue, carbohydrates and fat are by far the fuel of choice. While every cell is capable of burning glucose for energy, the same is not true for fat.


Our brain and red blood cells rely on the plentiful glucose in carbohydrates. Through gradual adaptation, the brain can learn to use fat in the form of ketone bodies, but our blood cells will always rely on glucose. In fact, our body fights really hard to keep our blood glucose levels within a narrow window. Once you dip below the minimum threshold of 20mg glucose/dL of blood you risk slipping into coma or having a seizure. This biological fact is partly what drives the daily recommendations for carbohydrates by major health organizations (see below).


  • The National Academy of Medicine sets the recommended dietary allowance at 130 grams per day. This is the minimum amount of carbohydrates needed to provide enough glucose for the brain and red blood cells from carbohydrates.
  • The 2015 Dietary Guidelines for Americans set the acceptable macronutrient distribution for carbohydrates at 45–65% of total daily calories. For someone who eats a typical 2,000-calorie diet, this is 225–325 grams of carbs per day — well above the RDA.
  • The World Health Organization and Food and Agriculture Organization recommend that 55% of total calories come from carbohydrates per day.


Carbs make up a large percentage of the U.S. food supply, contributing anywhere from 50–60% of calories since 1910. This makes sense given that the world’s staple crops are carb-heavy. These include cassava, corn, plantain, potato, rice, sorghum, soybean, sweet potato, wheat and yam. Fruits and vegetables, the foundation of a well-balanced diet, also contain carbohydrates. Even dairy contains milk sugar, which is a carb. Most modern societies base their diets on carbohydrate-rich foods.


Here’s where the argument that carbohydrates are essential starts to crumble:


The healthy human body is fully capable of reforming the amino acids from protein into glucose. Even the breakdown of fat for energy yields the tiniest bit of glucose. If an individual is eating enough calories, even if those calories are mostly from fat or protein, that person can still satisfy the glucose needs of their brain and blood cells and maintain their blood glucose at a normal level.


Nutrition science defines a nutrient as “essential” if we must get it from the diet because our body can’t make enough of it to meet our needs. Deficiencies in protein, essential fats (linolenic and linoleic), vitamins and minerals all match up to an impairment or disease. This same phenomenon doesn’t exist with carbohydrates.


Reach outside the literature, and it’s easy to obtain anecdotal evidence of people who survive on very low-carbohydrate diets. (Note that we’re not taking into account sustainability or personal happiness when subsisting on these diets.)

  • The Atkins diet advocates followers eat as little as 20 grams of carbohydrates per day! To give you an idea of what this means: 20 grams is the amount of carbs in 1 small (6-inch) banana.
  • The classic ketogenic diet is 80–90% fat. It was originally used as a therapy for epilepsy but is now gaining popularity for use in weight loss.
  • The traditional Inuit diet, which is what the natives of northern Canada subsisted on for many years, is empty of refined sugar and grains. Instead, there’s plenty of fresh seal, walrus and other marine life on the menu. A 1980s study of that diet found that it contained, on average, 23% calories from protein, 39% calories from fat and 38% calories from carbohydrates.



Carbohydrates (including fiber) don’t necessarily make the cut as “essential” nutrients, but they are very important. Eliminating carbs completely from the diet is not only impossible, it’s impractical. Fruits, vegetables, whole grains and dairy all contain carbs and are foundational to a healthful diet. When it comes to choosing how low-carb you should go, keep in mind that:

  • Everyone responds differently to varying levels of carbohydrates. Our bodies are unique, so what works for one person may not work for another. The key is to do some research, then experiment to figure out what works best for you. Enlisting expert guidance from a doctor or dietitian can make this process easier.
  • The best diet is one that can be followed over time. Consistency is key to a healthy lifestyle. Setting yourself up with a plan that allows 20 grams of carbs per day may not be the best way to achieve this. A balanced diet is one that allows flexibility for you to fit in foods you enjoy regardless of carbohydrate content.
  • “Low-carb” can be a healthy lifestyle. Most low-carb diets don’t go as low as you think, hovering around 35–40% of calories from carbohydrates. For many, the term “low-carb” has become synonymous with eating less refined carbs and added sugar and eating more fruits and vegetables. Needless to say, I’m on board with that!

Important Nutrients to Know: Proteins, Carbohydrates, and Fats


Proteins are often called the body’s building blocks. They are used to build and repair tissues. They help you fight infection. Your body uses extra protein for energy. The protein foods group includes seafood, lean meat and poultry, eggs, beans and peas, soy products, and unsalted nuts and seeds. Protein is also found in the dairy group. Protein from plant sources tends to be lower in saturated fat, contains no cholesterol, and provides fiber and other health-promoting nutrients.


Carbohydrates are the body’s main source of energy. The fruit, vegetables, dairy, and grain food groups all contain carbohydrates. Sweeteners like sugar, honey, and syrup and foods with added sugars like candy, soft drinks, and cookies also contain carbohydrates. Try to get most of your carbohydrates from fruits, vegetables, fat-free and low-fat dairy, and whole grains rather than added sugars or refined grains.

Many foods with carbohydrates also supply fiber. Fiber is a type of carbohydrate that your body cannot digest. It is found in many foods that come from plants, including fruits, vegetables, nuts, seeds, beans, and whole grains. Eating food with fiber can help prevent stomach or intestinal problems, such as constipation. It might also help lower cholesterol and blood sugar.

It’s better to get fiber from food than dietary supplements. Start adding fiber slowly. This will help avoid gas. To add fiber:

  • Eat cooked dry beans, peas, and lentils.
  • Leave skins on your fruit and vegetables but wash them before eating.
  • Choose whole fruit over fruit juice.
  • Eat whole grain breads and cereals that contain fiber.


Fats give you energy, and they help the body absorb certain vitamins. Essential fatty acids help the body function, but they aren’t made by your body—you have to consume them. Many foods naturally contain fats, including dairy products; meats, poultry, seafood, and eggs; and seeds, nuts, avocados, and coconuts.

Certain kinds of fat can be bad for your health—saturated fats and trans fats:

  • Saturated fats are found in the greatest amounts in butter, beef fat, and coconut, palm, and palm kernel oils. Higher-fat meats and dairy and cakes, cookies, and some snack foods are higher in saturated fats. Dishes with many ingredients are common sources of saturated fat, including pizza, casseroles, burgers, tacos, and sandwiches.
  • Trans fats, which is short for trans fatty acids, occur naturally in some foods but are also artificially produced. Because trans fats are not healthy, food manufacturers are phasing them out. But trans fats can still be found in some processed foods, such as some desserts, microwave popcorn, frozen pizza, margarine, and coffee creamer.

Fats that contain mostly trans fats and saturated fats are solid at room temperature. Limit your intake of saturated fats to less than 10 percent of your calories each day, and keep trans fat intake as low as possible.

Replace saturated and trans fats with these two types of healthier fats while keeping total fat intake within the recommended range:

  • Monounsaturated fats. These are found in the greatest amounts in canola, olive, peanut, sunflower, and safflower oils and in avocados, peanut butter, and most nuts.
  • Polyunsaturated fats. These are found in the greatest amounts in sunflower, corn, soybean, and cottonseed oils and in fatty fish, walnuts, and some seeds.

Oils contain mostly monounsaturated and polyunsaturated fats and are liquid at room temperature. These types of fat seem to lower your chance of heart disease when they replace saturated fats. But that doesn’t mean you can eat more than the Dietary Guidelines suggests.

To lower the saturated fat in your diet:

  • Choose cuts of meat with less fat and remove the skin from chicken
  • Use low-fat or fat-free dairy products
  • Choose oils, such as olive or canola, for cooking
  • Replace ingredients higher in saturated fats with vegetables, whole grains, low-fat and fat-free dairy products, or lean cuts of meats and poultry
  • Read the Nutrition Facts label and choose products lower in saturated fats

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Content reviewed: April 29, 2019

Carbohydrates: quality matters

What’s most important is the type of carbohydrate you choose to eat because some sources are healthier than others. The amount of carbohydrate in the diet – high or low – is less important than the type of carbohydrate in the diet. For example, healthy, whole grains such as whole wheat bread, rye, barley and quinoa are better choices than highly refined white bread or French fries. (1)

Many people are confused about carbohydrates, but keep in mind that it’s more important to eat carbohydrates from healthy foods than to follow a strict diet limiting or counting the number of grams of carbohydrates consumed.

What are carbohydrates?

Carbohydrates are found in a wide array of both healthy and unhealthy foods—bread, beans, milk, popcorn, potatoes, cookies, spaghetti, soft drinks, corn, and cherry pie. They also come in a variety of forms. The most common and abundant forms are sugars, fibers, and starches.

Foods high in carbohydrates are an important part of a healthy diet. Carbohydrates provide the body with glucose, which is converted to energy used to support bodily functions and physical activity. But carbohydrate quality is important; some types of carbohydrate-rich foods are better than others:

  • The healthiest sources of carbohydrates—unprocessed or minimally processed whole grains, vegetables, fruits and beans—promote good health by delivering vitamins, minerals, fiber, and a host of important phytonutrients.
  • Unhealthier sources of carbohydrates include white bread, pastries, sodas, and other highly processed or refined foods. These items contain easily digested carbohydrates that may contribute to weight gain, interfere with weight loss, and promote diabetes and heart disease.

The Healthy Eating Plate recommends filling most of your plate with healthy carbohydrates – with vegetables (except potatoes) and fruits taking up about half of your plate, and whole grains filling up about one fourth of your plate.

Try these tips for adding healthy carbohydrates to your diet:

1. Start the day with whole grains.
Try a hot cereal, like steel cut or old fashioned oats (not instant oatmeal), or a cold cereal that lists a whole grain first on the ingredient list and is low in sugar. A good rule of thumb: Choose a cereal that has at least 4 grams of fiber and less than 8 grams of sugar per serving.

2. Use whole grain breads for lunch or snacks.
Confused about how to find a whole-grain bread? Look for bread that lists as the first ingredient whole wheat, whole rye, or some other whole grain —and even better, one that is made with only whole grains, such as 100 percent whole wheat bread.

3. Also look beyond the bread aisle.
Whole wheat bread is often made with finely ground flour, and bread products are often high in sodium. Instead of bread, try a whole grain in salad form such as brown rice or quinoa.

4. Choose whole fruit instead of juice.
An orange has two times as much fiber and half as much sugar as a 12-ounce glass of orange juice.

5. Pass on potatoes, and instead bring on the beans.
Rather than fill up on potatoes – which have been found to promote weight gain – choose beans for an excellent source of slowly digested carbohydrates. Beans and other legumes such as chickpeas also provide a healthy dose of protein.

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83 the consumption of carbohydrates is most likely to

83 The consumption of carbohydrates is most likely to  lower the body’s set point. Incorrect  decrease blood glucose levels. Incorrect  reduce tension and anxiety. (True Answer )Correct  prevent bulimia nervosa. Incorrect  increase the basal metabolic rate. Incorrect 84 The level of serotonin in the brain is  decreased by a diet high in sugar. Incorrect  decreased by a diet high in salt. Incorrect  increased by a diet high in protein. Incorrect  increased by a diet high in carbohydrates. (True Answer )Correct  decreased by a diet high in calories. Incorrect 85 People’s preferences for sweet tastes are ________, and their preferences for excessively salty tastes are ________.  needs; incentives Incorrect  incentives; needs Incorrect  universal; learned (True Answer )Correct  learned; universal Incorrect  instinctual; conditioned Incorrect 86 A violent illness that follows our eating of a particular food is likely to influence our taste preferences. This illustrates that taste preferences are influenced by  basal metabolic rate. Incorrect  learning experiences. (True Answer )Correct  the binge-purge cycle. Incorrect  the settling point. Incorrect  drives and needs. Incorrect 87 People’s dislike of novel foods best illustrates  unit bias. Incorrect  neophobia. (True Answer )Correct  homeostasis. Incorrect  the refractory period. Incorrect

Carbohydrate’s direct impact is to raise blood sugar levels and therefore too much carbohydrate can cause problems for people with diabetes.

It would be wrong to label carbohydrate as inherently unhealthy as healthy people are able to handle a moderate amount of carbohydrate perfectly well.

However, the more insulin resistant you are, the less ability your body has to cope well with carbohydrate.

People with prediabetes and type 2 diabetes, in particular, will find that the more carbohydrate you have, the more likely you are to experience problems with the following:

A reduction in daily carbohydrate intake can address both weight gain and poor diabetes control.

  • High blood sugar levels
  • Increase in insulin resistance
  • Increasing body weight
  • Increased appetite

Warning : If you are on diabetes drugs that can cause hypoglycemia, you should not decrease carbohydrate intake unless your doctor is happy for you to adjust your carbohydrate intake.

Excessive carbohydrate intake

Whilst it’s difficult to prove that any one part of the diet is the responsible for conditions such as obesity and type 2 diabetes, there is growing evidence that excessive carbohydrate and sugar intake are playing a significant role in the development of these conditions.

A national survey into diets of low income households showed that some people are having very-excessive carbohydrate and sugar intakes. A significant proportion of under 50 year olds are eating between 500 and 600g of carbohydrate and over 300g of sugar each day.

A section of the 19-34 age group showed a worrying reliance on sugar with 68% of their energy intake coming from sugar alone.

Whilst this survey focused specifically on low-income households, it is likely that excessive carbohydrate and sugar consumption will also apply to a similar proportion of people in higher income households too.

What happens when carbohydrate is eaten

When carbohydrate is eaten, it gets broken down by digestion directly into glucose and is then absorbed into the blood.

The body then sends out insulin (unless you have type 1 diabetes) to move glucose out of the blood. Insulin will either move glucose into working cells such as the muscles or organs, or store the glucose as body fat.

More carbohydrate being eaten ultimately means there is more chance of having excess glucose that will need to be stored as fat.

Carbohydrate and high blood sugar

High carbohydrate intake and diabetes are not a good mix.

Because carbohydrate is converted directly into glucose, the majority of people with diabetes will struggle to achieve good sugar levels on a carbohydrate-focused diet.

The more refined carbohydrate in the food, the quicker and more sharply it will affect blood sugar levels. So, refined grains, such as white bread, white rice and any sugary foods, are likely to cause a sudden and dramatic rise in blood sugar.

Insulin resistance in people with type 2 diabetes means that the body will struggle to move sugar out of the blood. The more carbohydrate you have, the more the body will struggle and the higher your sugar levels will be.

Some people with type 1 diabetes may be able to manage a low-fat diet if they’re very good at managing their insulin but the truth is that most people with type 1 diabetes struggle to achieve adequate control on a carbohydrate-focused diet.

Carbohydrate and insulin resistance

Prediabetes and type 2 diabetes are conditions of glucose intolerance and therefore carbohydrate intolerance.

In prediabetes, and the first decade or so of type 2 diabetes, the body is over-producing insulin and this typically accompanies weight gain.

This over-production of insulin is the driver of insulin resistance and the development or progression of type 2 diabetes.

To work towards reversing this progressio, you need to turn down the insulin tap. As carbohydrate is the greatest stimulant of insulin production, it makes perfect sense to cut down on carbohydrate intake.

People with type 1 diabetes on a high carbohydrate diet may also develop insulin resistance. This is possible to detect if you notice you are injecting high amounts of insulin on a daily basis.

Carbohydrate and weight gain

Carbs are good, although certainly not essential, for providing energy to the muscles and organs.

In the modern age, though, most of us are not as active as society used to be in previous centuries. Desk work and machines have replaced much of the physical labour in and out of the homen, and transport has replaced much of our walking.

When people are active through the length of the day, carbohydrate based meals made more sense.

Muscles act as sugar stores and when we exercise, our muscles use these stores. Muscle use through the day would be emptied by exercise and re-filled with carbohydrate at the next meal.

These days, however, few of us empty our muscles of this stored sugar through the day. So, when we eat carbs, the glucose doesn’t get used to refill muscles, instead much of it gets stored away as body fat.

Insulin is the fat-storage hormone so, if you’re putting on weight, again the first thing to do is turn down the carb intake to turn down insulin and weight gain.

Carbohydrate and appetite

There have not been many scientific studies looking specifically at the effects of carbohydrate intake on appetite in people with diabetes.

A 2005 study indicates that lowering of carbohydrate intake helps reduce appetite, reduces energy intake and promotes weight loss in people with type 2 diabetes.

A low-carb diet may help reduce appetite because healthy, natural fat and moderate protein in the diet help provide energy in a more sustained way than carbohydrate.

Reducing insulin levels and switching the body to get its energy from ketosis, the burning of body fat, may also help towards reducing appetite through the day.

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