Do more specific plans help you lose weight? Examining the relationship between plan specificity, weight loss goals, and plan content in the context of a weight management programme

Abstract

Objectives: The conditions under which planning for behaviour change is most effective are not fully understood. In the context of a weight management intervention, we examined the interrelationship between plan specificity, type of behaviour planned (diet vs. exercise) and weight loss goals.  Design: Prospective design and content analysis of plans formed by participants of a 10-week weight management programme.  Methods: Participants (n=239) formulated two plans, for dietary and exercise behaviours respectively. Plans were rated for specificity by examining the number of plan components. Weight loss goals were assessed by asking how much weight participants intend to lose. Weight was measured objectively each of the 10 weeks. Changes in BMI over time and the interactions between plan specificity, and weight loss goals, for all plans and separately for diet and exercise, were estimated using linear mixed models.  Results: Plan specificity was unrelated to weight loss, but interacted with weight loss goals in predicting linear change in BMI (t= -2.48): More specific plans were associated with higher decreases in weight in participants with high weight loss goals. Separate interaction tests for plans formulated for diet and exercise change showed that more specific dietary plans, but not exercise ones, were associated with higher decreases in weight in participants with high weight loss goals (t= -2.21).  Conclusions: Within a population that is highly motivated to lose weight, the combination of high weight loss goals and formulating detailed plans for changing dietary behaviours may be most effective in supporting weight loss.