Increasing Exercise Is Not Associated With An Increase In Sedentary Time In Obese Adults

Abstract

BACKGROUND: It is now established that sedentary time is an independent predictor of morbidity and mortality. Whether increasing exercise is associated with an increase in objectively measured sedentary time is unclear. PURPOSE: To determine if increasing exercise consistent with consensus recommendations is associated with corresponding increases in sedentary time in abdominally obese adults. METHODS: Participants were 98 sedentary adults (BMI 31.8 ±3.7 kg/m2, age 55 ±7.1 years) randomly assigned to one of the following 4 groups: i) no-exercise control (n=19), ii) low-amount, low-intensity exercise (LALI) (180 and 300 kcal/ session for women and men, respectively, at 50% of VO2peak, n=24), iii) high-amount, low-intensity exercise (HALI) (360 and 600 kcal/session, respectively, at 50% of VO2peak, n=36), iv) high-amount, high-intensity exercise (HAHI) (360 and 600 kcal/session, respectively, at 75% of VO2peak, n=24). All exercise sessions were supervised. Sedentary time was determined objectively by accelerometry measured at baseline, 8, 16 and 24 weeks using established cut-points. RESULTS: The mean exercise time for LALI, HALI and HAHI were 31.2 ± 6.7, 58.3 ±7.8 and 42.7 ±4.5 min/day respectively. Corresponding values for sedentary time were 10.6, 10.3, and 10.4 hrs/day respectively. No statistically significant differences in sedentary time at baseline was observed between exercise groups (p=0.81). Similarly, no significant difference in the change in sedentary time at 24 weeks was observed between exercise groups (p=.59). The mean value for change in sedentary time for the 3 exercise groups combined was -15 mins/day. CONCLUSIONS: Increasing exercise consistent with consensus recommendations is not associated with a corresponding change in sedentary time independent of exercise amount or intensity. These observations counter the suggestion that fatigue associated with the adoption of exercise in obese adults may lead to corresponding increase in sedentary time.