Appetite and gut peptide responses to exercise and calorie restriction. The effect of modest energy deficits

Weight loss is the result of a sustained negative energy balance, which is typically achieved by decreasing food intake and/or increasing physical activity. Current evidence suggests that acute energy deficits of ~4820kJ elicit contrasting homeostatic responses when induced by exercise and food restriction but the response to government-recommended energy deficits is unknown. Twelve healthy men (mean(SD): age 24(5) years, body mass index 23.8(2.7)kg{dot operator}m^-2, maximum oxygen uptake 55.4(9.1)mL{dot operator}kg^-1{dot operator}min^-1) completed three 8h trials (control (Con), exercise-induced energy deficit (Ex-Def) and food restriction (Food-Def)) separated by 1week. Thirtyminutes of cycling at 64.5(3.2)% of maximum oxygen uptake was performed in Ex-Def from 0 to 0.5h, which induced an energy deficit of 1469(256)kJ. An equivalent energy deficit was induced in Food-Def (1478(275)kJ) by reducing the energy content of standardised test meals at 1h and 4h. Appetite ratings, acylated ghrelin and peptide YY_3-36 concentrations were measured throughout each trial. An ad libitum meal was provided at 7h. Appetite was higher in Food-Def than Ex-Def from 4 to 8h (P=0.033) and tended to be higher across the entire 8h trial (P=0.059). However, energy intake at the ad libitum meal did not differ between trials (P=0.634; Con 4376 (1634); Food-Def 4481 (1846); Ex-Def 4217 (1850)kJ). Acylated ghrelin was not related to changes in appetite but plasma PYY_3-36 concentrations were higher in Ex-Def than Food-Def (P<0.05) and negatively correlated with changes in appetite across the entire 8h trial (P=0.037). An energy deficit of ~1475kJ stimulated compensatory increases in appetite when induced via calorie restriction but not when achieved by an acute bout of exercise. Appetite responses were associated with changes in plasma PYY_3-36 but not acylated ghrelin concentrations and did not influence subsequent energy intake.