Associations Between 24 H Movement Behaviors and Body Weight in Postpartum Women: An Isotemporal Substitution Model Approach

TL;DR

This study explores how reallocating time between daily activities like sleep, exercise, and sitting affects body weight in women after childbirth.

Contribution

The study introduces isotemporal substitution models to analyze how shifting time between movement behaviors influences postpartum weight.

Findings

Replacing moderate-to-vigorous physical activity with light activity or sleep was linked to lower body weight in early and mid-postpartum.

Substituting sedentary time with light physical activity reduced body weight, especially in early postpartum.

Enough sleep (≥7 hours) was crucial for weight loss benefits when reallocating time to light physical activity.

Abstract

Background/Objectives: There are limited data on the dynamic changes in daily composition of movement behaviors (sleep; moderate-to-vigorous physical activity, MVPA; light physical activity, LPA; and sedentary time, SED) and their associations with body weight in postpartum women. The purpose of this study was to examine associations of reallocating time in one behavior to another with body weight, at different times in the first year postpartum. Methods: The study included 86 women who delivered a singleton infant at ≥37 weeks gestation. Physical activity and sleep were measured via actigraphy in early, mid-, and late postpartum. Body weight was measured at each timepoint. Isotemporal substitution models were used to examine the association of reallocating ten minutes of one behavior (MVPA, LPA, SED, or sleep) to another, with body weight. Results: Participants spent most of their day in SED (~52–53%), followed by sleep (~30%), LPA (~12–13%), and then MVPA (~2%) throughout the first year postpartum. In early and mid-postpartum, but not late postpartum, reallocating 10 min of MVPA to LPA, SED, or sleep was associated with lower body weight (range: 3.07–4.03 kg lower). In early and late postpartum, reallocating 10 min of SED to LPA was associated with a lower body weight (4.03 kg and 1.04 kg, respectively). In participants who slept ≥7 h per day, reallocating sleep to LPA in early postpartum, and MVPA time to LPA in mid-postpartum was associated with lower body weight. In those who slept <7 h, no significant associations with body weight were found when reallocating time from one behavior to another. Conclusions: Encouraging LPA throughout the postpartum period may be beneficial for weight loss, and having enough sleep may be especially important for early to mid-postpartum. Future research examining the impact of changes in LPA on body weight in the postpartum period are needed, along with postpartum specific 24 h movement guidelines.

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