Objective: To examine the effects of exercise on short term energy intake and to investigate the existence of exercise-induced anorexia.
Design: Two studies were conducted, both with three treatment conditions and employing a repeated measures design.
Setting: The Human Appetite Research Unit at Leeds University Psychology department.
Subjects: Twenty three healthy, lean male subjects (n = 11 and n = 12 respectively) were recruited from the student/staff population of Leeds University.
Interventions: Subjects were randomly assigned to a control, low intensity and high intensity exercise treatment in the first study and to a control, short duration and long duration exercise treatment (high intensity) in the second. Motivation to eat was measured by visual analogue rating scales and by the length of the time between the end of exercise and the volitional onset of eating. Energy and macronutrient intakes were measured by means of a free-selection test meal and by recorded intakes for the next 2 days.
Results: Subjective feelings of hunger were significantly suppressed during and after intense exercise sessions (P 0.01), but the suppression was short-lived. Exercise sessions had no significant effect on the total amount of food consumed in the test meal but intense exercise delayed the start of eating (P < 0.05). When energy intake was assessed relative to the energy expended during the exercise or control periods, only the long duration, high intensity session created a significant short-term negative energy balance (P < 0.001).
Conclusions: These studies indicate that exercise-induced anorexia can be characterized by a brief suppression of hunger, accompanied by a delay to the onset of eating. The temporal aspects of exercise-induced anorexia may best be measured by the resistance to begin eating rather than the amount of food consumed.