Low carbohydrate diet may not lead to impaired physical performance. Allowing a period of adaptation, supplementing sodium and potassium to your low carbohydrate diet and having just 15-25% of the total calories coming from proteins can provide unimpaired physical performance.
It is a common knowledge that carbohydrates must be a major component of your daily energy intake for optimal physical performance. Follower of low carbohydrate diets frequently complain of light headedness, weakness and fatigue.
Most experiments that assess the performance impact of low carbohydrate diets usually lasted for a maximum 1 week. During this period, the subject’s performance, usually the endurance, would be compared before and after the low carbohydrate diet. The results showed that low carbohydrate diets decreased the performance of individuals.
In one remarkable study in 1930s, Dr Eugene DuBois, studied 2 explorers under constant observation for 3 months, after which they were allowed more freedom of movement. The study showed that the explorers survived 12 months in good health with no signs of scurvy or other deficiencies, on low carbohydrate diets that derived 80-85% of calories from fat and only 15-20% from proteins.
During 1970s, low calorie ketogenic diets gained a lot of interest due to its weight loss effects. However, there were cases of fatigue and cardiac dysfunction that were in stark contrast of the conclusions of Dr. Eugene DuBois. At this time, Dr. George Cahill demonstrated that a number of weeks were required for the body to adapt to the removal of carbohydrate. They also found that as the subjects were literally fasting, they had to be provided potassium and sodium supplements as Inuit diets has these minerals already in their diets. Their conclusion was that the endurance of the subjects decreased in the 1st week of low carb diet and was gained back by the 6th week of the low carb diet. This regain of endurance could not have been possible without excellent preservation of functional tissues such as skeletal muscles, heart, lungs and blood. This study has not been refuted so far.
One important point to note is that when people go on low carbohydrate diet, they should stay on the diet for longer than 3 weeks and should not take any ‘cheat’ meal of carbohydrates. Even a slight increase in carbohydrate will result in fatigue.
Excerpts from Nutrition and Metabolism 2004
Article: Ketogenic Diets and Physical Performance
Author: Stephen D Phinney