Acute effects of exercise intensity on subsequent substrate utilisation, appetite, and energy balance in men and women.

Abstract

Exercise is capable of influencing the regulation of energy balance by acutely modulating appetite and energy intake coupled to effects on substrate utilization. Yet, few studies have examined acute effects of exercise intensity on aspects of both energy intake and energy metabolism, independently of energy cost of exercise. Furthermore, little is known as to the gender differences of these effects. One hour after a standardised breakfast, 40 (19 female), healthy participants (BMI 23.6 ± 3.6 kg·m-2, V̇O2peak 34.4 ± 6.8 mL·kg-1·min-1) undertook either high-intensity intermittent cycling (HIIC) consisting of 8 repeated 60 s bouts of cycling at 95% V̇O2peak or low-intensity continuous cycling (LICC), equivalent to 50% V̇O2peak, matched for energy cost (∼950 kJ) followed by 90 mins of rest, in a randomised crossover design. Throughout each study visit, satiety was assessed subjectively using visual analogue scales alongside blood metabolites and GLP-1. Energy expenditure and substrate utilization were measured over 75 min postexercise via indirect calorimetry. Energy intake was assessed for 48 h postintervention. No differences in appetite, GLP-1, or energy intakes were observed between HIIC and LICC, with or without stratifying for gender. Significant differences in postexercise nonesterified fatty acid concentrations were observed between intensities in both genders, coupled to a significantly lower respiratory exchange ratio following HIIC (P = 0.0028), with a trend towards greater reductions in respiratory exchange ratioin males (P = 0.079). In conclusion, high-intensity exercise, if energy matched, does not lead to greater appetite or energy intake, but may exert additional beneficial metabolic effects that may be more pronounced in males.