Abstract
Energy balance is important for weight maintenance with exercise having documented physiological, behavioural, and appetite effects. Exercise is known to acutely influence appetite but evidence for an independent effect of intensity is lacking. The purpose of this dissertation was to investigate the role of exercise intensity on appetite and energy intake (EI), energy expenditure (EE), and the metabolic effects of exercise intensity per se in lean and overweight individuals and to determine whether there was influence of gender or differences between groups. Forty healthy volunteers (30 lean and 10 overweight) undertook 2 periods of exercise matched for energy cost, (i) 8 repeated 60 second bouts of cycling at 95% VO2 max; high intensity exercise (HI) and (ii) 30 minutes of continuous cycling, at a fixed cadence, at 50% VO2 max; low intensity exercise (LI) in a randomised cross-over design. Satiety to a standard meal was assessed subjectively using visual analogue scales. Ad libitum intake was measured 3-h post-breakfast and for 2 days post-exercise. EE and fat oxidation were measured every 30 mins post-exercise. The results showed that in the lean group relative to LI, HI suppressed prospective food consumption, increased EE (P=0.001), fatty acid (NEFA) utilisation (P=0.004) and fat oxidation (P<0.001), but did not affect appetite, EI, plasma glucose, insulin, GLP-1 or lipid levels post-exercise. There was a differential effect of gender on prospective food consumption and NEFA response post-exercise. HI increased EE and fat oxidation post-exercise for men. In the overweight individuals, HI did not differ from LI in terms of appetite, GLP-1, glucose, insulin, lipid or NEFA levels, with no difference in EI, EE and fat oxidation post-exercise. In conclusion, there are different consequences of exercise intensity in short-term control of energy balance depending on BMI and gender; our results support the need for longer term intervention to test these mechanisms.