A Low Carb Diet for Athletes?


Have you been hearing stories that fats are better than carbs for fuel for endurance athletes? Maybe you have wondered if scientific research supports those stories?  To find the latest science, I attended the annual meeting of the American College of Sports Medicine (ACSM). ACSM is an organization with more than 26,000 exercise physiologists, sports nutrition researchers, and sports medicine professionals—all of whom are eager to share both their research and extensive knowledge. At this year’s meeting in San Diego (May 2015), I was able to verify that carbohydrates are indeed, the preferred fuel for all athletes. The following information highlights some of the research on carbohydrates for athletes.

  • Louise Burke PhD RD, Head of Sports Nutrition at the Australian Institute of Sport, verified that carbs are indeed an essential fuel for athletes who train hard and at high intensity. That is, if you want to go faster, harder, and longer, you’ll do better to periodise your eating around these hard training sessions with carb-based meals (pasta, rice) rather than with meat and a salad doused in dressing—a high protein and fat meal. Carbohydrates (grains, vegetables, fruits, sugars, starches) get stored as glycogen in muscles and are essential fuel for high-intensity exercise. Athletes with depleted muscle glycogen experience needless fatigue, sluggishness, poor workouts, and reduced athletic performance. (These complaints are common among my clients who mistakenly limit carbs, believing they are fattening. Not the case. Excess calories of any type are fattening!)

Clearly, the amount of carbohydrate needed by an athlete varies according to length and intensity of exercise. Fitness exercisers who train at low or moderate intensity need fewer carbs to replace muscle glycogen stores than do elite athletes who do killer-workouts. Ultra-marathoners who do long, slow, “fat-burning” runs can get away with a lower carb intake – unless they want to be able to surge up a hill or sprint to the finish.

  • A study with Cross-Fit athletes (think Paleo Diet) who reduced their carb intake simultaneously reduced their ability to perform as well during their high-intensity workouts. Those who ate less than 40% of their calories from carbs (≤3 g carbs/pound body weight/day or