Low-Carb Diet

14 Dec 2013

In the last few years feeding strategies that are low in CHO have been successfully adopted by athletes in ultra-endurance events (Ironman, ultra marathons etc), in order to enhance the use of fat as fuel to sustain longer performance. 

Even some road cyclists have experienced low-carb diets, but the results were always somewhat disappointing in terms of competitive performance. 

A recent publication "The art and science of low carbohydrate performance"by JS Volek and S.D. Phinney proposed again the theoretical and practical bases of this particular diet. 
The authors assume that a diet rich in CHO forces the athlete to a real DEPENDENCE from carbohydrates as fuel in performance, and we all know that the stores of glycogen can provide a little more than 2000 Kcal, while the fat deposits of an athlete with 7% of body fat are able to provide an amount of energy that is about 20 times higher. 

Reducing the CHO intake to less than 50g per day the body would get used to use fat as fuel in just 2-3 weeks, thereby allowing the intake of high amounts of fats (even saturated) without cardiovascular risks. 
In addition to the few carbohydrate (<200 Kcal ), the diet in fact provides for the intake of 1.0-1.5 g/kg of protein (280 - 400Kcal), while the rest of the required energy is provided by fats. 
The diet creates a state of physiological nutritional KETOSIS, between 1 and 3 mMoles, bringing forth the possible advantages already explained in my previous article dated November 16th, 2013. 

The authors state that athletes that are "Keto-adapted" can attain a lipidic power under effort equal to 2 g/min, whereas athletes of similar fitness fed with diets rich in CHO only achieve less than 1 g/min (see also my article dated December 15th, 2004). 

120g of fats in 1 hour (2g/min) equal 1080 Kcal: a considerable energy resource, but not outstanding, corresponding to a cyclist riding and producing about 300 watts. 
This power output largely covers the performance required in ultra-endurance events, but is insufficient to ensure the demands of top level cyclists, who express power outputs of 400 watts and beyond for dozens of minutes. 
This explains why low-carb diets have not been successful in road cycling races: the reduced availability of CHO does not allow athletes to express the high power required by the accelerations and the different paces of competitions. 

Nevertheless a slightly hypocaloric regimen and low-carb can also be useful to the rider in the pre-racing season period in order to lose excess body fat by forcing the use of lipids as an energy source and establishing a ketosis, which also has suppressive effects on appetite, helping to sustain the caloric restriction.