S. E. Tomten, A. T. Høstmark in Scand J Med Sci Sports 2006: 16:127–133
Exercising female athletes create an energy deficit with exercise for which they require an increase in energy intake to match expenditure and remain in a state of energy balance. However, reported daily intake is often similar to, or even lower than sedentary women; which creates an energy deficit leading to menstrual dysfunction and related complications such as poor bone health. In a study by Tomten and Hostmark, energy balance, nutritional intake, training activity and total energy expenditure were assessed in female athletes both with and without menstrual dysfunction. Energy balance and nutritional adequacy were assessed in a group of runners with irregular menstrual function (IR, n=10) as well as a group of runners with normal menstrual function (R, n=10). Daily training-related excess energy expenditure and total energy expenditure (TEE) were not different between groups. Daily energy intake (EI) was, however, significantly lower in IR athletes than in the R athletes. EI and TEE were in balance in R athletes; however, a significant negative energy balance was observed in IR athletes. The energy deficit observed in the IR athletes was corroborated by significantly lower levels of free thyroxine in IR athletes, which may indicate a depressed BMR in IR athletes. Mean intakes of carbohydrates and protein were close to recommended guidelines and were not significantly different between groups. The key difference in macronutrient intake was observed in dietary fat that was significantly lower in the IR athletes. Though all athletes were weight stable, an energy deficit was observed in IR athletes, and not in R athletes, primarily due to a lower intake of dietary fat. Fear of gaining weight has been widely accepted as a probable cause for a sub-optimal EI in athletes who depend on a low body mass for success. Decreasing dietary fat intake has been one method by which female athletes lower their EI to maintain low body weights. They may be reluctant to increase food intake in fear of a possible weight gain, even though a higher EI may seem to improve the reproductive function, it may also increase body weight and fat mass.