Background Many participants in behavioral weight loss (BWL) programs struggle to meet the moderate-to-vigorous physical activity (MVPA) prescription. Elucidating momentary predictors of MVPA in BWL programs could improve targeting of risk/protective factors, which may boost MVPA adherence and enhance weight control; yet this remains unstudied.Purpose To examine momentary factors as potential predictors of MVPA intentions, behavior, and the intention-behavior gap among BWL participants.Methods Participants (N = 116) were adults with overweight/obesity in a 12-week remote BWL intervention that prescribed 150 minutes of MVPA/week. Participants wore Fitbits (measuring MVPA) and received 6 daily ecological momentary assessments (EMA; brief, smartphone-delivered surveys) for 2-week periods at treatment initiation, mid-treatment, and end-of-treatment. EMA measured MVPA intention and 11 potential predictors of MVPA intentions/behaviors (based on empirical support from non-BWL contexts). Multilevel models tested within-person relations between predictors and MVPA outcomes, controlling for survey number per day, weekday/weekend status, and assessment period.Results Stress, tiredness, and pain/discomfort negatively predicted MVPA intention, whereas energy, positive affect, a positive social interaction, self-control, self-efficacy, and self-compassion positively predicted MVPA intention. Tiredness negatively predicted MVPA behavior, whereas energy, positive affect, self-control, body satisfaction, and self-efficacy positively predicted MVPA. Tiredness also predicted increased odds of an intention-behavior gap.Conclusions This study identified 9 momentary predictors of MVPA intentions, 6 predictors of MVPA engagement, and 1 predictor of the MVPA intention-behavior gap in a BWL program. These findings identify potential intervention targets, and momentary digital interventions may try to modify or provide support around these factors in real-time to facilitate MVPA.
Behavioral weight loss (BWL) programs prescribe moderate-to-vigorous physical activity (MVPA) to help individuals with obesity achieve weight loss, but participants often struggle to meet MVPA goals. Identifying predictors of MVPA may help BWL programs better support participants in achieving MVPA. This study examined if factors that change moment-to-moment, including psychological and physical states (eg, mood or pain), predict when a BWL participant intends to engage in MVPA and actually engages in MVPA. When BWL participants experienced higher levels of stress, tiredness, and pain, they were less likely to set MVPA intentions, but when they experienced higher levels of positive mood, energy, self-control, body satisfaction, and self-efficacy (belief in their ability to achieve goals), they were more likely to set MVPA intentions. Also, when BWL participants were more tired, they engaged in less MVPA, but when they had higher energy, positive mood, self-control, body satisfaction, and self-efficacy, they engaged in more MVPA. Finally, when BWL participants were more tired, they were less likely to follow through with their MVPA intentions. Findings may help improve BWL programs that track these psychological or physical states through digital technology (eg, smartphones) and send support when someone is at risk of not meeting MVPA goals.