OBJECTIVE: There is substantial variability in the effectiveness of group lifestyle interventions for weight loss. We examined associations between intervention weight loss counselors and participant weight loss and program engagement in a structured lifestyle intervention. METHODS: Data were from 575 adults (87% female, 51 (12) years, baseline BMI: 32.4 (7.2) kg/m2) in an 11-week structured group lifestyle program. Participants self-enrolled in groups led by 11 weight loss counselors based on meeting times. All weight loss counselors received the same training. Linear mixed models were used to evaluate counselor predictors of participant percent (%) weight loss and program engagement (weight reporting throughout 11 weeks). RESULTS: Of the 575 participants, 415 (72%) defined as complete reporters, i.e. reported weight weekly, lost a mean 7.3% weight (range: +3.1% to 16.2%). Participant weight loss differed between weight loss counselors (p = 0.003), and adjusted mean participant weight loss by weight loss counselor ranged from 6% to 9%. Weight loss was greater for weight loss counselors with a graduate degree in nutrition than weight loss counselors with another graduate degree (8.3% versus 6.4%, p = 0.05), but was not different between weight loss counselors with and without graduate degrees. Higher counselor BMI was associated with higher participant weight loss (p = 0.005). CONCLUSIONS: These results demonstrate the potential for quantitatively important effects of weight loss counselor characteristics on participant success and engagement in structured lifestyle interventions, indicating a need for research in this area.
