Background

In overweight adults, moderate-to-vigorous physical activity (MVPA) is countered by behavioral (eg. increased appetite and sedentary behaviors, reduced light intensity activity, LIPA) and physiological (eg. reduced resting metabolic rate, RMR) adaptations that resist increases in total energy expenditure (TEE). Recent data showed that spreading microbouts of MVPA across the day acutely inhibits appetite, increases MVPA without lowering LIPA, suggesting it may increase TEE and lead to weight loss over time. We compared the effect of 4-wk of microbouts of MVPA on energy balance components to that of 4-wk of single bouts of MVPA matched for total active time.

Methods

19/28 sedentary overweight adults (7M/12F, age: 33±8 y, BMI: 29.5±3.3 kg/m2) were randomly assigned to a 4-wk intervention consisting of brisk walking for either 5 min/hr for 9 hrs, 5 d/wk (MICRO, n=10), or 45 min/d, 5d/wk (ONE, n=9). Before and during the last two weeks of the interventions TEE, activity energy expenditure (AEE) and RMR were measured by doubly labeled water and indirect calorimetry. Time spent sedentary and active was assessed with ActiGraph GT3X and ActivPAL. Body composition (isotopic dilution) and self-perceived appetite (VAS) were measured pre and post intervention. Diet was uncontrolled.

Results

Both MICRO and ONE had high compliance (89±12% and 79±15%, respectively) and similarly impacted energy balance components. The increase in MVPA (p=0.09) and decrease in time spent sedentary (p=0.03) were associated with reduced LIPA (p=0.01). RMR rose (p=0.03) likely due to an increase in fat-free mass (p=0.07). TEE, AEE and appetite remained unchanged. Body and fat mass did not change, indicating stable energy balance.

Conclusions

Contrary to our hypothesis, frequent microbouts of activity does not increase TEE, reduce appetite or induce weight loss, at least over 4 weeks. This strategy does not impact energy balance better than the traditional single continuous bouts of MVPA.