Adherence

Higher self-efficacy for eating and exercise behaviors prospectively predicts greater engagement in weight control behaviors (adherence, effort, monitoring) during active treatment, which in turn mediates weight loss.

Your confidence in your ability to stick to your plan matters, but only because it drives your actual actions. To lose weight, you must build self-efficacy by successfully executing specific behaviors like monitoring calories and sticking to exercise plans. The paper proves that self-efficacy only leads to weight loss if it translates into these concrete actions; believing you can do it is not enough—you must do it.