Objectives
The conditions under which planning for behaviour change is most effective are not fully understood. In the context of a weight management programme, 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 body mass index (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 plans, 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.