The effect of replacing sedentary behavior by different intensities of physical activity in body composition: a systematic review

Abstract

Introduction: The isotemporal substitution model (ISM) is a statistical approach that estimates the effects of replacing, in minutes, a block of physical activity or sedentary behavior by another block with different intensity. Previous studies have used the ISM to evaluate the effect of different isotemporal substitutions on body composition. Thus, the ISM can contribute to the understanding of changes in body composition related to distinct lifestyles and, hence, guiding future recommendations for maintaining and/or improving body composition. Objective: To review the effect of replacing sedentary behavior by physical activity on body composition change analyzed through ISM. Methods: Original articles in English were identified from searches in PubMed and Periódicos Capes databases. The search was carried out by two researchers. Last search was performed in October 2020. Results: A total of 17 included articles, which evaluated different applications of ISM in relation to body composition change, mostly obtained by BMI and body fat. The physical activity was mainly assessed by using an accelerometer. Several methodological differences among the included studies limited comparisons between findings, including the sample profile and cut off points for physical activity. Conclusion: Among the studies that evaluate the effect of replacing sedentary behavior for different intensities of physical activity through ISM, replacing sedentary behavior by moderate-to-vigorous physical activity presented a more consistent effect in body composition change in comparison to replacement by other physical activity intensities, even for small blocks of time (five minutes).