Reduced serum cholecystokinin response to food intake in female athletes

Strenuous training in women has been shown to cause menstrual dysfunction and decreased bone mineral density. These endocrine and metabolic complications are associated with an insufficient dietary intake and decreased body fat content in female athletes. The present investigation was undertaken to study serum levels of cholecystokinin (CCK), insulin, gastrin, and cortisol in 14 female long-distance runners and 15 sex- and age-matched control subjects during intake of a standardized meal (500 kcal). The athletes showed a decreased response of the "satiety peptide" CCK to the meal and reported increased hunger compared with the control group. Meal-related insulin response was also decreased in the athletes, whereas gastrin levels were comparable to those of controls. Basal levels of glucose were increased in the athletes, but there was no difference in postprandial levels between the groups. Cortisol levels were clearly elevated in the female runners. We conclude that insufficient food intake in female athletes cannot be explained by increased CCK secretion and satiety. Since the athletes reported a larger caloric intake of a normal daily breakfast than the control subjects, the decreased CCK response may instead be explained by an adaptation to increased food intake. The decreased meal-related insulin response may be a reflection of increased insulin sensitivity as an adaptation to physical exercise. However, an impaired peptide secretion cannot be excluded. The role of elevated cortisol levels in the gastrointestinal hormone response needs further investigation.