Effects of fasting on endurance exercise in adult males: preliminary evidence for a "nocebo" effect

The literature has repeatedly reported a negative effect of fasting on endurance exercise in humans. The goal of this study was to test the hypothesis that endurance performance is susceptible to a “negative placebo” or “nocebo” effect of early (24-h) fasting. Twelve physically-fit, young adult males performed an endurance performance test under each of three conditions: after a 24-hour fast (A), after a 24-hour fast ingesting non-caloric liquid meals (B), and in the postabsorptive state (C). The tests consisted of pedalling the maximum distance in 60 minutes on a cycle ergometer at 2 kpm, and were separated by a minimum of one week. Subjects were allocated randomly to the different treatment condition orders. Plasma glucose and triglycerides were measured before and after each performance test. Performance was significantly lower (pA and A<B (p