Essentials of Nutrition for Sports

If only 40% of her calories consumed that day come from
carbohydrate, full glycogen replacement cannot be achieved.

More Carbohydrate—To a Point

Keep in mind that although carboh

ydrate has been studied for

decades, the role of intramuscular fat is relatively poorly studied. Normally, about 2,500 calories are stored as intramuscular fat.

Typical of many refueling studies, one recent study showed that

increasing calories from 57% carbohydrate to 68% or 88% carbohydrate results in more muscle glycogen after repeated bouts of exercise, in proportion to the amount of carbohydrate ingested.

Although both the 68% and 88% carbohydrate diets increased

intramuscular glycogen, the 88% carbohydrate diet led to decreased muscle triglyceride concentrations.

Absolute Carbohydrate Calories

It is commonly accepted that most aerobic endurance athletes

should consume a diet relatively high in carbohydrate—65% to 70% of total caloric intake.

Many find this approach simplistic, and say it is more important

to ingest enough carbohydrate calor

ies to replace those lost through

exercise. This often amounts to the same thing, but reflects an approach to the reasoning underlying the simplification. For example, it is not that an athlete consuming 4,000 calories per day needs 65% of calories from carbohydrate; it is that 7-10 grams per kilogram per day—up to 2,400 carbohydrate calories for a 132-pound (60 kilogram) athlete—are needed to replace those lost during exercise.

Studies show that although athletes are able to get the percentage

right, based on 7-10 grams per kilogram per day, less than 20% of men and women athletes cons

umed enough carbohydrate.

What Do Scientific Studies Show?

If you look at scientific research, you have to look at research

designed to answer the right questions.

Are you a RAAM rider looking to improve fat metabolism? Are

you a weekend warrior? Are you a recreational rider, riding a few times a week at no more than 75% of your maximum heart rate? Are you a frequent high-end training and racing athlete?

The literature supporting high-carbohydrate diets for high-end

aerobic endurance athletes is massive, international, and accepted.

The literature supporting higher-fat diets is small. The only study

I was able to find concerned athletes who consumed a meal of high (45%) fat vs. low (20%) fat the night before a cycling ergometer test. The riders were rested, were not subject to previous glycogen depletion, and had no breakfast.

40–30–30 proponents often quote this study, saying that it shows

the superiority of increasing fat in the athlete’s diet. One could just as easily say it supports the notion of eating breakfast!

Diet and Health

The current medical wisdom is that reducing fat in our diets is

important for general health. It is

believed that fat contributes to

heart disease and cancer. Fortunately, the high-carbohydrate diet for athletes achieves these very aims.

Insulin and High-Carbohydrate Diets

Proponents of a higher fat diet (for example, the 40–30–30 diet)

point to diabetes and “carbohydrate poisoning.” They claim that high loads of carbohydrate are associated

with high insulin levels. They

say that insulin contributes to the conversion of carbohydrate to fat, and that increased fat stores contribute to insulin resistance and diabetes. Therefore, so the argument goes, we should reduce our intake of carbohydrate.

Nutrition for Sports, Essentials of 50