Does habitual physical activity increase the sensitivity of the appetite control system? A systematic review

Background: It has been proposed that habitual physical activity (PA) improves appetite control; however the evidence has never been systematically reviewed. Objective: To examine whether appetite control (e.g. subjective appetite, appetite-related peptides, food intake) differs according to levels of PA. Data sources: Medline, Embase and SPORTDiscus were searched for articles published between 1996-2015 using keywords pertaining to PA, appetite, food intake and appetite-related peptides. Study selection: Articles were included if they involved healthy non-smoking adults (18-64 years) participating in cross-sectional studies examining appetite control in active and inactive individuals; or before and after exercise training in previously inactive individuals. Study appraisal and synthesis: Of 77 full-texts assessed, 28 studies (cross-sectional = 14; exercise-training = 14) met the inclusion criteria. Results: Appetite sensations and absolute energy intake did not differ consistently across studies. Active individuals had a greater ability to compensate for high-energy preloads through reductions in energy intake compared to inactive controls. When PA level was graded across cross-sectional studies (low, medium, high, very high), a significant curvilinear effect on energy intake (z-scores) was observed. Limitations: Methodological issues existed concerning the small number of studies, lack of objective quantification of food intake, and various definitions used to define active and inactive individuals. Conclusions: Habitually active individuals showed improved compensation to the energy density of foods, but no consistent differences in appetite or absolute energy intake, compared to inactive individuals. This review supports a J-shaped relationship between PA level and energy intake. Further studies are required to confirm these findings. PROSPERO registration number: CRD42015019696 Key points: • Habitual physical activity and appetite control are not independent of each other; they are inter-connected. • The relationship between physical activity and energy intake is J-shaped. • Objective assessment of all components of energy balance is necessary to improve understanding of this relationship.