Distinguishing early patterns of physical activity goal attainment and weight loss in online behavioral obesity treatment using latent class analysis

Abstract

Physical activity (PA) goal adherence is consistently associated with greater weight loss during behavioral obesity treatment, and early weight loss response predicts future weight loss success. However, it remains unclear which behaviors during the initial weeks of treatment distinguish responders from nonresponders and might be effective targets for improving treatment outcomes. To characterize subgroups with distinct patterns of PA goal adherence during the initial 2 months of an online, group-based weight control program and determine associations between these patterns and 6-month weight loss. Participants received an online behavioral obesity intervention with PA goals and daily self-monitoring. Weekly adherence to step goals and moderate-to-vigorous PA (MVPA) minute goals based on self-monitoring records were examined using latent class analysis. Body weight was objectively measured at 0, 2, and 6 months. Participants (N = 212; 91.5% female, 31.6% race/ethnic minority, mean body mass index: 35.8 ± 5.9 kg/m2) clustered into three subgroups based on early goal attainment: “Both PA Goals,” “MVPA Goals Only,” and “Neither PA Goal.” The “Both PA Goals” class had significantly greater 6-month weight loss (estimated mean weight loss [95% CI]: −9.4% [7.4 to 11.5]) compared to the “MVPA Goals Only” (−4.8% [3.4 to 6.1]) and “Neither PA Goal” classes (−2.5% [1.4 to 3.6]). Individuals meeting both PA goals early in treatment achieve greater weight losses than those meeting MVPA but not step goals, pointing to the need to explore factors associated with nonadherence to each of the PA goals to better understand these potential targets for treatment refinement and adaptive interventions.

Identifying Predictors of Adherence to the Physical Activity Goal: A Secondary Analysis of the SMARTER Weight Loss Trial

“…We did not measure baseline PA levels before the introduction of Fitbit trackers and thus, the potential moderating effects of baseline PA on future PA levels could not be assessed. Moreover, we did not personalize prescribed PA goals based on baseline PA levels or first week PA goal attainment, which may have resulted in participants who were adherent to the PA goal being prescribed smaller PA goals than their initial PA levels and missing “the critical window” for improving PA (21,28). Similar to our study, previous lifestyle interventions have demonstrated the importance of monitoring short-term intervention response measures, such as PA goal attainment at 2 months (21) and weight loss at 8 wk (28) to long-term PA goal attainment.…”

“…Moreover, we did not personalize prescribed PA goals based on baseline PA levels or first week PA goal attainment, which may have resulted in participants who were adherent to the PA goal being prescribed smaller PA goals than their initial PA levels and missing “the critical window” for improving PA (21,28). Similar to our study, previous lifestyle interventions have demonstrated the importance of monitoring short-term intervention response measures, such as PA goal attainment at 2 months (21) and weight loss at 8 wk (28) to long-term PA goal attainment. In general, not meeting the short-term behavioral goals could be indicative of participants’ poor response to the intervention or lack of engagement and the need for developing additional strategies to support participants with low PA goal attainment.…”

“…We equated Fitbit-provided PA measures, i.e., fairly active and very active minutes as to MVPA based on the respective MET cut-points—3–6 METs and >6 METs. Weekly MVPA minutes were computed by summing MVPA equivalents, i.e., fairly and very active minutes per week, dividing by the number of days with the valid data and multiplying by 7 d to account for potential underrepresentation of true PA goal adherence (21). The primary outcome for this study was average percentage of adherence to the study-defined PA goal of ≥150 min·wk −1 of MVPA over the 52 wk.…”

“…The percent of adherence to the PA goal for the first week was computed as weekly MVPA minutes relative to the PA goal of ≥150 min•wk −1 of MVPA and multiplied by 100%. We included short-term intervention response variables, such as percent weight loss for week 4, the percentage of days adherent to the calorie goal for the first week, and the percentage of adherence to the PA goal for the first week as potential predictors of long-term adherence to the PA goal, as meeting behavioral goals early in the study has been shown to predict long-term PA goal attainment in mHealth weight loss trials (21,28).…”

“…A number of systematic reviews have reported that the use of wearable activity trackers had a positive impact on PA goal achievement in lifestyle interventions (10,11,(13)(14)(15)(16)(17)(18)(19)(20). However, the use of wearable activity trackers appears to be short-term (13,15,16) and may be more effective among older adults (18), men (13), adults with low body mass index (BMI) (19), those with high adherence to the PA goal at 2 months into an intervention (21), and those with chronic conditions (16). Finally, questions remain on the long-term effectiveness of behavioral interventions using wearable activity trackers for PA promotion and factors that may moderate the effectiveness of tracker-supported interventions.…”