Carbohydrates have been known to be the universal fuel for physical activity and a necessity to prevent lean mass reduction. Recent studies have been tackling this subject and have shown that a Very Low Carbohydrate Diet (VLCD) can still preserve lean body mass or increase it in case of exercise and in fact has no detrimental effect on athletic performance. (1)
Numerous studies have taken elite athletes and put them under the test of VLCD or ketogenic diets to explore their outcomes.
A study published last year in the Sports Science for Health Journal, put 6 master endurance athletes on a 4 week low carbohydrate diet and found there was no change in time trial performances. (2) Another study published just earlier this year, found that a carbohydrate restricted diet followed by a strength training athlete had no effect on their strength and power levels despite a reduction in their body mass. (3) Regarding their athletic performance stats, athletes were not affected.
The endocrinology department at Boston University compared the effects of a normal diet versus a low carbohydrate diet on 55 subjects for a 12 week period. The results showed that Low Carbohydrate diets may be more beneficial to cardiovascular health and inflammation than a diet with a regular amount of carbohydrates. The scientist found lowered levels of inflammatory markers including C-reactive protein, and an elevated health promoting markers such as serum adiponectin and high density lipoprotein-cholesterol. (4)
More in depth investigations have been done by Volek and his team in the department of kinesiology at the University of Connecticut. This team of scientist assessed the body composition and hormonal responses in a comparative study between 20 subjects. Those that followed the carbohydrate restricted diet showed no significant changes in glucagon, total or free testosterone, sex hormone binding globulin (SHBG), insulin-like growth factor-I (IGF-I), cortisol, or triodothyronine (T3) uptake, nor were there significant changes in body composition or hormones in the restricted carbohydrate group. (5)
However it's not all good news, a study published in the American Journal of Kidney Disease concluded that the consumption of a low carbohydrate diet delivers a marked acid load to the kidney, increases the risk for stone formation, decreases estimated calcium balance, and may increase the risk for bone loss with healthy subjects. (6)
After reviewing the available publications up till now, the concept of the sole reliance on carbohydrates as a fuel for exercise is slowly changing. Yet, the metabolic effects of such dietary restriction needs more investigation at least within the athletic community since the influence of exercise is important on human physiology.
1) Manninen, Anssi H. "Metabolic effects of the very-low-carbohydrate diets: misunderstood "villains" of human metabolism." J Int Soc Sports Nutr 1.2 (2004): 7-11.
3) Sawyer, Jason C., et al. "EFFECTS OF A SHORT-TERMCARBOHYDRATE RESTRICTED DIET ON STRENGTH AND POWER PERFORMANCE." Journal of strength and conditioning research/National Strength & Conditioning Association (2013).
4) Ruth, Megan R., et al. "Consuming a hypocaloric high fat low carbohydrate diet for 12weeks lowers C-reactive protein, and raises serum adiponectin and high density lipoprotein-cholesterol in obese subjects." Metabolism (2013).
5) Volek, Jeff S., et al. "Body composition and hormonal responses to a carbohydrate-restricted diet." Metabolism 51.7 (2002): 864-870.
6) Reddy, Shalini T., et al. "Effect of low-carbohydrate high-protein diets on acid-base balance, stone-forming propensity, and calcium metabolism." American Journal of Kidney Diseases 40.2 (2002): 265-274.