Background/objectives: Positive associations have been found between adherence and weight loss in behavioral weight-management interventions. However, less attention has been given to the level of adherence needed to reach clinically significant weight loss. This study examined the levels of adherence associated with a ≥ 5% - < 10% or ≥ 10% weight loss in a community-based, intensive behavioral weight management program, Weight Watchers® (WW), which included three modes of access: (1) 24-weekly WW meetings over 6 months, (2) the WW member website, and (3) the WW mobile application.
Methods: A total of 292 participants were randomized to a WW (n = 147) or a self-help (SH) (n = 145) condition. To assess the impact of adherence, only participants in the WW condition were included in analyses (n = 147). Adherence was defined as use of the three modes of access. Measured heights and weights were obtained at baseline and 6 months. Receiver-operating characteristic curve analyses were conducted to determine the minimal level of adherence associated with clinically significant weight loss.
Results: In a 6-month period, increased likelihood of achieving a weight loss ≥ 5% - < 10% was associated with attending approximately one-third (35.4%) of weekly meetings, use of the member website about 25% of days, and use of the mobile application 16.1% of days. Attendance at approximately two-thirds (64.5%) of meetings, use of the member website 41.6% of days, and use of the mobile application 14.7% of days were associated with a clinically significant weight loss of ≥ 10%. Meeting attendance was the strongest predictor of weight loss at 6 months.
Conclusions: Although adherence to a behavioral weight management program was an important predictor of weight loss, extremely high levels were not needed to achieve clinically significant weight loss. These results are important to help patients and treatment providers understand realistic goals for weight management.