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Evidence Summary

Underlying Theory: Theoretical constructs are taken from a number of theories, with the main theories being Social Cognitive Theory and the Transtheoretical (Stages of Change) Model. Because this is a behavioral weight loss program, principles of motivational interviewing were also included.

Strategies Used:  The Weight-Wise intervention’s approach is an adaptation of the Diabetes Prevention Program for which there is strong evidence of its effectiveness at improving health behaviors and reducing weight. Strategies included the following:

Research Findings or Evaluation Outcomes:  In the initial test of the intervention’s effectiveness, researchers recruited and enrolled women with a BMI of 25-45 in a randomized controlled trial comparing the intervention to a wait-listed control group. The study sample included 143 women (71 in the intervention and 72 controls). The intervention was delivered at a single site by one individual who was employed by the research team. Researchers measured weight, body mass index, cholesterol, blood pressure, quality of life, depressive symptoms, social support, family functioning, dietary risk, and self reported minutes of physical activity.  Findings were analyzed using an intention to treat analysis and analysis of covariance adjusting only for baseline weight. In addition, data were reported on attendance, whether women were keeping records of their physical activity and dietary intake, and program acceptability. Average session attendance for the weight loss phase  was 65% (median of 14 sessions attended); 88% (126/143) completed follow-up weight measurement. In a subsequent translation study, the researchers are testing the effectiveness of Weight-Wise when it is implemented by existing staff in six North Carolina county health departments.

Intervention Effect: The initial test of the intervention’s effectiveness in a single site found that the between group difference in weight loss was 9.5 lb (4.3 kg) (p < .0001), and over half of participants lost 8 or more pounds.  When the relationship between attendance and weight loss outcomes were analyzed, data demonstrated a dose-response relationship (i.e., women who attended more sessions lost more weight).  Participants in the intervention group, as compared to the control, also had greater reductions in body fat and blood pressure, improvements in dietary intake, and increases in moderate physical activity. Cost per participant in the intervention group was $242, compared to $976 per person for the Diabetes Prevention Program (Hernan et al. 2003). Although the goals of DPP are different from those of Weight-Wise; these findings demonstrate that when adapted from an individual level intervention to a group-format the intervention remained effective at reducing weight while also reducing costs per participant.