Which is Better? High Fat or High Carb Diets?

The consensus among many exercise physiologists Is that levels of muscle glycogen are directly related to muscle endurance capacity hence, the espousal of the high carbohydrate diet. However, there has been a recent trend toward a diet higher in fat due to the suggestion that increasing one's fat Intake may actually aid performance.

A recent study (RD. Starling et al., "Effects of diet on muscle triglyceride and endurance performance," Journal of Applied Physiology, 82:1185-89, 1997) examined such a relationship. Scientists asked seven endurance-trained men to ingest two different diets: 1) high cash (83% of calories from carbohydrates) and 2) high fat (68% of calories from fat). The two diets were composed of identical amounts of calories eaten over a 12-hour period. After the 12 hours, the test subjects performed self-paced intervals of cycling, which were terminated when the individual expended approximately 400 calories.

The researchers discovered that after the subjects consumed the high-fat diet, it took longer to reach the conclusion of the cycling trial than after they consumed the high-carb diet. These results suggest that the Ingestion of a high-fat diet the day before an endurance type workout does net help performance on the contrary, it actually inhibits performance. The question, however, is how a long-term high-fat diet affects performance, as opposed to a short-term high-fat diet, as in these studies.

Outside of the possible effect on cardiovascular disease, how well con the human body adapt to eating high-fat fore? Bodybuilders would be wise to stick to a more moderate approach.