The Cooper Institute

Founded in 1970 by the "Father of Aerobics"
Kenneth H. Cooper MD, MPH


Dietary Carbohydrate: Facts and Misconceptions

Posted in
Eat better

Tuesday, Sep 05, 2017

With national diabetes month approaching, this is a good opportunity to discuss facts as well as a few misconceptions regarding dietary carbohydrate.

First, the basics: carbohydrate is one of 6 essential nutrients required by the human body for survival. All carbohydrates contain 4 calories per gram. During the digestive process, dietary carbohydrate is broken down into glucose, which then leaves the intestines and enters the blood. Glucose is a major energy source for all cells of the human body; particularly the brain and spinal cord as well as red blood cells.  When the body consumes extra carbohydrate, some of the excess is stored as glycogen in muscle and liver cells. Glycogen is best thought of as tens of thousands of glucose molecules bonded together. When muscle and liver cells reach their capacity for storing glycogen, the remainder of the excess carbohydrate is converted to fatty acids and stored in adipose tissue. So far, nothing that has been stated is the least bit controversial. You will find this basic information in all nutrition and medical textbooks.

Now let’s dig a little deeper. There are two broad categories of dietary carbohydrate; simple and complex. Simple carbohydrates are synonymous with simple sugars, which are found in high concentrations in foods and beverages such as non-diet soda, candy, honey, syrup, sports drinks and energy drinks, doughnuts, pastry, cookies, and cakes. Many of these products are referred to as empty calorie foods; which simply means that they have very low nutritional value. You just won’t find many vitamins, minerals, phytochemicals (non-nutrients in plant-based foods that help prevent disease) or much fiber in most foods and beverages that are high in simple carbohydrate. While lacking in fiber, 100% fruit juice is a notable exception to this rule. Complex carbohydrates are plant-based foods, and include things such as fruits, vegetables, whole grains, and legumes (beans, peas, and peanuts). Unlike simple carbohydrates, complex carbohydrates pack quite a wallop nutritionally speaking. They are loaded with fiber, vitamins, minerals, and phytochemicals. With the exception of fruit, most complex carbohydrates are also a significant source of dietary protein. People are usually very surprised to learn that! So whenever we speak of dietary carbohydrate, it’s very important to distinguish the simple from the complex.

So how much dietary carbohydrate should you consume each day?  That depends on the individual. The 2015-2020 Dietary Guidelines for Americans recommend that 45-65% of total daily calories should come from carbohydrate; with most of that in the complex form. If you have metabolic syndrome, you should consume the lower end of the recommended range. On the other hand, if you are highly physically active each day, you may need to consume closer to the upper end of the recommended range. Unless you have a particular health condition, the overwhelming majority of qualified health professionals would suggest that you stay within the recommended range of 45-65%. You may be wondering at this point how many total calories that you should consume each day. That number is determined primarily by your age, gender, height, weight, and physical activity level. You can get a good estimate of your total daily calorie requirement by using this link. 

Please note that this estimate is based on wanting to maintain your current body weight. If you wish to lose weight, you should subtract about 300-400 calories per day from the estimate.

Can too many carbs make you fat?  Sure. Our body weight status is dictated by the number of calories we consume each day versus the number of calories we expend. Consuming too much of anything (even the healthy stuff!) can result in weight gain if we wind up consuming more calories each day than we expend. It’s extremely important to focus on the quality as well as the quantity of carbohydrate that we take in each day. By limiting simple carbohydrates and emphasizing complex carbohydrates in our diet, we significantly decrease our risk for developing type 2 diabetes, as well as cardiovascular disease, diverticulitis, and some cancers.  These risks can be decreased further by becoming more physically active and achieving a reasonable body weight.

What about very low carb diets?  These diets recommend getting only ~10-15% of total daily calories from carbohydrate, which generally speaking, is not a good idea for most people. Such an approach will likely lead to short-term weight loss, but there is little to no evidence that these diets result in long-term weight control or improved health for most individuals. The very low carb diet has been around for over 50 years and tens, if not hundreds of millions of people have tried it. If this approach actually resulted in long-term weight control, then why are 70% of American adults currently overweight or obese? 

So, to summarize:

  • Dietary carbohydrate is essential to human survival and disease prevention 
  • Dietary carbohydrate exists in two broad categories; simple and complex
  • Most simple carbohydrates are nothing more than empty calories        
  • Complex carbohydrates are plant-based foods that are loaded with nutrients, fiber, and phytochemicals.  Most complex carbs are also a good source of protein!
  • All dietary carbohydrate is converted to glucose during digestion
  • The RDA for carbohydrate is 45-65% of total daily calories
  • There is little to no scientific evidence that very low carbohydrate diets lead to long-term weight loss or improved long-term health

Note: The Cooper Institute has recently published a state of the art textbook titled Principles of Health and Fitness for Fitness Professionals. This book is an absolute must for fitness leaders, and is a great resource for anyone who is seeking to earn a nationally accredited personal trainer certification! Click on the links above to learn more.