It's true that insulin is needed for the transport of glucose into adipose cells, where it can be converted into triglyceride, the storage form of fat. This only happens to carbohydrate surplus to requirements for immediate energy production and for glycogen synthesis. Also, research has found that the process of converting carbohydrate to fat is actually rather inefficient. In experiments, 94% of fat calories consumed are stored as fat, compared to 80% of carbohydrate stored under similar conditions.


Don't be frightened of insulin
The final verdict has to be that the best dietary strategy for an endurance athlete is to eat a high-carbohydrate diet. An elevated level of circulating insulin after eating carbohydrate is nothing to worry about - it's actually highly beneficial, as it encourages cells to store away glycogen. When the crunch comes during exercise, the body is capable of switching its metabolism to favour fat and glycogen breakdown, providing ready availability of glucose and free fatty acids.

Although there are no direct research results referring to the Sears dietary system, a study of some relevance was carried out by Walberg and co-workers (International Journal of Sport Medicine, Vol 9 (4), pp 261-266). Nineteen male weightlifters were put on two different low-calorie diets, one with high protein and moderate carbo content, the other with moderate protein and higher carbo. On the high protein diet, muscular endurance was diminished.

Janet Pidcock