Objective: To examine the effects of two types of vigorous exercise [cycling (CYC) and running (RUN)] and diet composition on appetite control.
Design: Two studies using separate groups of subjects were used for the two forms of exercise. The studies used a 2 x 2 design with the factors being exercise and diet composition. Therefore both studies had four treatment conditions and used a repeated measures design.
Setting: Both studies took place in the Human Appetite Research Unit at Leeds University.
Subjects: Twenty-four lean, healthy males were recruited from the student staff population of Leeds University.
Interventions: For both studies a control (no-exercise) and a vigorous exercise session (70% VO2 max) was followed by a free-selection lunch comprising high-fat/low-carbohydrate foods or low-fat/high-carbohydrate foods, during which energy and macronutrient intake was monitored. Motivation to eat was measured by visual analogue scales and by the latency to volitional onset of eating. Energy intake for the remainder of the day (outside of laboratory) was monitored by providing the subjects with airline-style food boxes.
Results: Both CYC and RUN produced similar effects on appetite responses. Both CYC and RUN induced a transitory suppression of hunger (P < 0.01 and P < 0.05) and a delay to the onset of eating (P < 0.001). Exercise (whether CYC or RUN) had no significant effect on the total amount of food eaten, but there was a significant effect of lunch type. When provided with the high-fat/low-carbohydrate foods energy intake was significantly elevated (CYC: P < 0.001; and RUN: P < 0.0001). Both types of exercise induced a short-term negative energy balance when followed by the low-fat/high-carbohydrate foods (P < 0.001), which was completely reversed (positive energy balance) when subjects ate from the high-fat/low carbohydrate foods.
Conclusions: These results indicate that eating high-fat foods can prevent exercise inducing any (short-term) negative energy balance. Therefore, in order for exercise to have a significant impact on weight control, it is important to consider the energy density of the accompanying diet. Despite the different physiological aspects of cycling and running, they did not display different effects on appetite.