Objective: To examine the effects of a high dose (two high-intensity exercise sessions) of exercise on energy intake (EI) and subjective states (hunger and mood).
Design: Using a within subjects design, there were two treatment conditions, each of two consecutive days.
Setting: The Human Appetite Research Unit at Leeds University Psychology Department.
Subjects: Eight lean males who were regular exercisers were recruited from the student/staff population of Leeds University.
Interventions: The effects of the high dose of exercise Ex1 were compared with the effects on the day immediately after exercise (Ex2) and two consecutive days of no exercise (R1 and R2). EI was monitored using self-record food diaries and subjective states were tracked using a new Electronic Appetite Rating System (EARS). Heart rate and physical activity were also measured.
Results: Feelings of hunger were not elevated by the high dose of exercise on Ex1 or on the day after exercise (Ex2). In fact, average daily feeling of hunger on Ex1 was significantly lower compared with the average daily feeling of hunger on Ex2 (t = 3.15, d.f. = 7, P < 0.05), but not when compared with R1 or R2. EI and macronutrient intakes were not different on Ex1, Ex2, R1 or R2. Therefore, there were no increase in EI on Ex1 or Ex2 to account for the measured increase in exercise-induced energy expenditure (1200 kcal). Continuously monitored heart rate and activity profiles indicated that there was no difference in activity during the non-exercise periods between the four days.
Conclusions: This study indicates that a high dose of exercise in one day failed to have any effect on EI within the same day or on the day immediately after exercise, compared with days of no exercise. These results demonstrate that an acute but substantial increase in energy expenditure (EE) due to intense exercise does not automatically increase hunger or EI within 48 h. This indicates the absence of any strong coupling between EE and EI in the short-term, probably as a result of food intake being held in place by environmental contingencies and short-term pre-absorptive physiological responses arising from eating itself.