Metabolic responses to preexercise meals containing various carbohydrates and fat.

After a 12-h fast six different meals (potatoes, rice, sucrose solution, potatoes+margarine, rice+margarine, and a confectionery bar), each containing 0.7 g carbohydrate/kg body wt, were consumed 30 min before exercise (n = 9). During the 30 min immediately after ingestion, the glycemic and insulinemic responses to the meals distinguished these foods into two groups: 1) high glycemic (ie, potatoes, sucrose, confectionery bar) and 2) moderate glycemic (ie, rice, potatoes+margarine, rice+margarine). After 20 min of moderate-intensity exercise, plasma glucose declined in all carbohydrate trials to values of 3.4 +/- 0.1 mmol/L, which were significantly (P < 0.05) lower than values after subjects fasted (4.2 +/- 0.2 mmol/L). Therefore, the glycemic and insulinemic responses to these meals were independent of their carbohydrate classification of simple or complex and the addition of fat reduced the glycemic and insulinemic responses. However, despite these different responses before exercise, all of the meals caused plasma glucose to decline to equally low concentrations early in exercise.