Exploration of Interindividual Variability for Change in Waist Circumference and Body Weight in Response to Standardized Exercise
BACKGROUND: Substantial interindividual variability in response to a standard dose of exercise exists independent of the trait under investigation. Whether interindividual variability attributed to exercise exists after accounting for random variability is unknown. OBJECTIVE: To determine the magnitude of the interindividual variability in response to exercise for waist circumference (WC) and body weight (BW) after accounting for random variability and, the extent to which the variability is explained by lifestyle behaviors. METHODS: Participants were 181 (61% female) sedentary, abdominally obese adults (mean, (SD); 53, (7.5) years) who completed a 24-week intervention. Participants were randomly assigned to: control (n=44) or 5 weekly sessions of low amount, low intensity (LALI) (180 and 300kcal/session for women and men respectively at 50% V02peak, n=46); high amount, low intensity (HALI) (360 and 600kcal/session for women and men respectively at 50% V02peak, n=53); or high amount, high intensity (HAHI) (360 and 600kcal/session for women and men respectively at 75% V02peak, n=38). Adherence was ≥ 80% in all exercise groups. Physical activity (PA) performed outside of the prescribed exercise was measured by accelerometer. Daily self-report diet records were used to derive energy intake (kcal) and diet quality (Canadian-Healthy Eating Index-2010, Mediterranean Score). The variability in response to exercise (SDR) was determined by separating the random variability from the intervention variability by comparing standard deviations (SD) from both the control and intervention groups. RESULTS: WC and BW were substantially reduced at 24 weeks in all exercise groups compared to control (P<0.01). The variability due to exercise (SDR) for change in WC was 3.1, -0.3 and 3.1 cm for LALI, HALI and HAHI groups respectively. Corresponding values for BW were 3.8, 2.0 and 3.5 kg for LALI, HALI and HAHI respectively. No dietary or PA variable was identified as a determinant of the interindividual variability in response to exercise for WC or BW (p>0.05). CONCLUSION: A substantial interindividual variability in response to exercise was observed for change in WC and BW after accounting for the random variability. The determinants of the heterogeneity in response to exercise remain to be determined.