I am an emeritus professor of exercise science, and in the spirit of academic debate, I would like to respond to a recent article in the Herald’s Food and Nutrition section entitled “
I feel that the advice given in this article is misleading at best and irresponsible at worst.
The article advises athletes to switch their diet to higher fat, lower carbohydrate (CHO) intake to become “fat adapted.” The theory is that this metabolic shift would enable athletes to utilize fat as fuel rather than CHO.
Glycolysis shows us that glucose is the only fuel for anaerobic exercise and there is anaerobic exercise even in endurance aerobic events.
Distance runners need to fuel anaerobically to run up a hill, increase their pace to pass a competitor, etc. CHO is the only fuel for that.
In addition, metabolizing a blend of CHO and fat is more efficient in terms of O2 consumption and this blend is used for fuel in the overwhelming majority of exercise bouts. Glycogen, the stored form of glucose, also stores almost three grams of water for every gram of glycogen, helping to satisfy the all-important hydration needs for endurance events.
Since “bonking” or “hitting the wall” is a function of the total depletion of CHO, I fail to see how reducing already limited glycogen stores reduces the potential of that event occurring. It would only bring the “bonk” on sooner.
CHO loading or glycogen super compensation is a long, well established protocol and proven advantage for athletes. There may be reasons for reducing CHO intake and attempting fat adaptation, but athletic performance is not one of them. The only possible exception might be ultra-marathon running; however, the overwhelming majority of exercise activities and events fall far below that type of extreme endurance.
Jim Cross
Durango
