Carbohydrate Confusion

Carbohydrates commonly get a bad rap in the media; with low - carbohydrate diets common among the weight loss community. But is there evidence to support this? What is the ideal amount of carbohydrates to include for health and/or weight loss? Luckily, one of the Registered Dietitians from Revolution Physical Therapy Weight Loss is here to clear up some confusion about carbohydrates.

Carbohydrates, protein and fat are the three macronutrients. According to the 2015 Dietary Guidelines for Americans, carbohydrates should make up 45-65% of one’s intake. In comparison, protein should make up 10-30% of one’s intake and fat should be 25-35% of one’s intake(1). As you can see, carbohydrates are needed in the most abundant amount - over half of one’s calories.

Sources of carbohydrates include fruits, vegetables, grains, dairy products and any added sugars (sugar sweetened beverages, desserts, etc). Carbohydrates are fuel for our body. Carbohydrates break down into glucose in our blood, which our cells utilize as energy.

So what’s the story behind low carbohydrate diets and weight loss?

Most studies investigating low-carbohydrate diets restrict carbohydrate intake to 20 grams/day (this is equivalent to 1 medium banana) and most are done for a short period of time (< 6 weeks) so limited long-term research is available(2,3).

Among the limited evidence, decreasing carbohydrates has been shown to produce some weight loss (2,3). However, this is primarily due to water weight. Carbohydrates are stored in the form of glycogen in the liver and muscle tissue. Glycogen is stored with water so when we decrease carbohydrates in our diet, the body breaks down the glycogen and releases water. When someone starts eating a moderate amount of carbohydrates again, the weight gain seen is just the water weight(4).

While short-term weight loss may be possible, long - term weight loss is more difficult with this regimen due to several factors. Several food groups have to be eliminated on a low-carbohydrate diet (any grains, fruits, starchy vegetables, dairy, and any added sugars). This can lead to nutrient deficiencies. Fiber is one nutrient that would be significantly reduced; which can lead to constipation, diverticulitis and colon cancer; just to name a few(5).

Furthermore, significantly reducing carbohydrates means that protein and fat will be significantly increased. This unbalanced macronutrient ratio can lead to other health problems. Increased saturated fat consumption can have a detrimental impact on cardiovascular health. Increased protein intake can have detrimental effects for those at risk for kidney disease(4). Sticking close to the percentages recommended by the Dietary Guidelines for Americans helps ensure that one is getting all the necessary nutrients for optimal health.  

So, what does this mean?

In order to have optimal energy levels, it’s important to include carbohydrate sources that are energy dense, provide fiber and other vitamins and minerals. Focusing on fibrous carbohydrates and/or complex carbohydrates (whole fruits, vegetables, whole grains, fat-free or low-fat dairy) is important in order to provide sustainable energy. Simple carbohydrates (added sugars, desserts, refined grains) metabolize very quickly, resulting in a quick energy spike and should be limited. While the quality of carbohydrates matters, so does the portion. Utilizing the MyPlate visual can be helpful in determining portions of carbohydrates to include at each meal.

Carbohydrates provide various health benefits and should comprise 45-65% of one’s intake. At Revolution Physical Therapy Weight loss, the Registered Dietitian’s work with patients to determine their individual calorie and carbohydrate goals to promote health and weight loss. If you have any further questions, consult with a Registered Dietitian at Revolution Physical Therapy Weight Loss to determine your individual goals.


  1. Dietary Guidelines for Americans 2015-2020.  

  2. Krebs, NF, et al. Efficacy and Safety of a High Protein, Low Carbohydrate Diet for Weight Loss in Severely Obese Adults. The Journal of Pediatrics.

  3. Brehm, BJ, et al. A Randomized Trial Comparing a Very Low Carbohydrate Diet and a Calorie-Restricted Low Fat Diet on Body Weight and Cardiovascular Risk Factors in Healthy Women. Journal of Clinical Endocrinology and Metabolism: 88(4).

  4. Sherman, WM. Muscle Glycogen Storage and it’s Relationship to Water. Int J Sports Med.

  5. Anderson, JW, et al. Health Benefits of Dietary Fiber. Nutr Rev. 2009. Apr:67(4): 188-205.