Effects of meeting steps-based and minutes-based physical activity goals on weight loss in online behavioral weight control: seemingly unrelated regrassion analysis

Background: Behavioral weight loss programs often prescribe physical activity (PA) goals in terms of minutes/week of moderate-to-vigorous PA (MVPA) and steps/day. However, the impact of meeting each type of goal prescription on weight loss is unclear, particularly in digitally-based (eHealth/mHealth) programs. This secondary analysis of a randomized trial examined the effects of meeting steps-based and minutes-based goals on weight loss in an eHealth behavioral weight control program. Methods: Adults in the control arm received a 6-month online behavioral weight loss intervention with prescribed weekly goals for daily steps and minutes of MVPA. The number of weeks steps-based and minutes-based goals were met (>= 100% and >= 75% thresholds) based on self-reported PA were examined as predictors of 6-month weight loss among those providing weight outcomes (n = 172; 81% of control arm) using a systems regression approach. Results: Participants (BMI 35.6 kg/m(2); 90.1% female; 48.7 years of age) met weekly goals for MVPA (7.1 +/- 6.4 weeks) more often than steps (3.5 +/- 5.5 weeks, P < .001). Meeting the steps goals (beta = .24, P < .001) and MVPA goals (beta = .20, P < .001) were each statistically significant predictors of weight loss at the 100% threshold; their total effects were not statistically different from one another (X-2 = 1.12, P = .29). Similarly, at the 75% threshold for steps goals (beta = .19, P < .001) and MVPA goals (beta = .19, P < .001), each independently predicted weight loss; no differences were detected in their total effects (X-2= .01, P= .92). The probability of reaching >= 59% weight loss was comparable between meeting the steps goals and MVPA goals at both adherence thresholds. Conclusions: Greater attainment of PA goals prescribed as steps and minutes of MVPA independently contribute to similar weight loss outcomes in a 6-month online behavioral weight loss intervention. Future research should determine whether promoting adherence to combined steps-based and minutes-based goals produces better weight loss than utilizing either goal alone and identify strategies that improve adherence.