Accepted for/Published in: JMIR mHealth and uHealth
Date Submitted: Oct 30, 2020
Date Accepted: Feb 26, 2021
Associations of physical activity level and variability with 6-month weight change in a real-life study among 26,935 users of connected devices
ABSTRACT
Background:
Physical Activity (PA) is a modifiable lifestyle factor that can be targeted for increasing energy expenditure and promoting weight loss. However, results regarding the efficient PA amount for weight loss remain heterogeneous. Wearable activity trackers constitute a valuable opportunity to obtain objective measurements regarding PA and study large populations in real-life settings.
Objective:
We aimed to study the associations of 1) objectively-assessed PA characteristics (PA level and variability) and 2) their evolution with six-month weight change.
Methods:
We analyzed data from 26,935 Withings connected device users (wearable activity trackers and digital scales). We used the monthly mean of daily step values as a proxy for PA level and derived the monthly coefficient of variation (CV) of daily step values to estimate PA level variability. Associations between PA characteristics and six-month weight change were assessed using multivariable linear regression analyses controlled for age, sex, blood pressures, heart rate, and the predominant season. Restricted cubic spline regression was performed to better characterize the continuous shape of the associations between PA characteristics and weight change. Secondary analyses were performed by analyzing the six-month evolution of PA characteristics in relation with weight change.
Results:
Our results revealed that both a greater PA level and a lesser PA level variability were associated with weight loss. Compared with individuals who were initially in the sedentary category (<5,000 steps/day), low active (5,000–7,499), somewhat active (7,500–9,999), and active (≥10,000) individuals had a 0.21 kg, a 0.52 kg, and a 1.17 kg greater decrease in weight, respectively (95%CI: -0.36,-0.06; 95%CI: -0.70,-0.33; 95%CI: -1.42,-0.93). We also observed that each 1,000 steps/day increase in PA level over the six-month follow-up was associated with a 0.26 kg (95%CI: -0.29,-0.23) decrease in weight. No association was found between the six-month change in PA level variability and weight change.
Conclusions:
Our results add to the current body of knowledge that health benefits can be observed below the 10,000 steps/day threshold and suggest that not only increasing mean PA level is important, but also that greater regularity of PA level, irrespectively of PA level, may play an important role for short-term weight loss.
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