Abstract
OBJECTIVE: To investigate the effects of breaking up prolonged sedentary behavior (SB) on daily movement behavior and energy balance in adults with overweight/obesity. METHODS: Thirty participants (16F/14M; 34.2±7.3y; 29.5±3.2kg/m (2) ) were randomized to either BREAK (nine hourly 5-min brisk walking bouts) or a duration-matched intervention, ONE (45-min brisk walking), both performed 5 days/week for 6 weeks. Pre- and post-intervention, daily SB and physical activity (PA; accelerometry), body composition (doubly labeled water [DLW]), total daily energy expenditure (TDEE; DLW), appetite, and fasting leptin were measured. Linear-mixed effects models tested time effects and time-by-group interactions. RESULTS: Only BREAK reduced prolonged SB (-8%; interaction: p=0.043). Both groups shifted SB-PA composition toward greater moderate-to-vigorous PA with proportional reductions in SB and light PA (time: all p≤0.011), which were associated with increases in TDEE (+0.67 MJ/d; time: p=0.040). Body and fat mass increased in ONE only (interaction: p=0.061 and p=0.055). No differences were noted in energy intake, appetite, or leptin levels. CONCLUSIONS: Spreading short PA bouts throughout the day increases MVPA and TDEE to the same extent as a traditional continuous PA bout. Future studies should investigate whether minor differences in body composition are driven by distinct behavioral/physiological compensations influenced by the daily pattern of PA/SB. STUDY IMPORTANCE QUESTIONS: What is already known about this subject? Acutely, breaking up prolonged sedentary behavior (SB) with short bouts of physical activity (PA) increases energy expenditure and reduces food cravings compared to a single continuous PA bout.Single continuous PA bouts have been associated with compensatory reductions in non-exercise activities (daily living activities) in some studies, which may attenuate increases in total daily energy expenditure (TDEE) and limit effects on body mass and adiposity. What are the new findings in your manuscript? Performing brisk walking either through frequent, short bouts spread across the day or as a single continuous bout over 6 weeks increases moderate-to-vigorous PA (MVPA) at the expense of SB and light PA and increases TDEE to a similar extent in adults with overweight or obesity.However, only the frequent, short active breaks reduced time spent in prolonged SB (>60 min), an independent cardiometabolic health risk factor.Despite no differences in energy intake, appetite, or plasma leptin concentration, the single continuous bouts were associated with a small, non-robust increase in body and fat mass, whereas these remained stable in the active breaks group, suggesting differential compensatory adaptations. How might your results change the direction of research or the focus of clinical practice? Promoting frequent, short bouts of PA throughout the day can improve daily movement and help meet current PA/SB guidelines to a similar extent as traditional PA strategies, while also reducing prolonged sedentary time.This strategy may help limit compensatory responses sometimes observed in response to continuous MVPA bouts, offering a new tool to manage body weight.However, differences in body composition outcomes were small and not robust, and future studies are needed to determine whether these patterns translate into meaningful long-term effects on energy balance and weight regulation.