Does better planning hold the promise to achieving weight loss? Practitioners and academics often prescribe planning one's diet and exercise as a means of achieving weight loss. However, this study challenges such a prescription. The key insight derived from experience-rich qualitative data with a sample of dieters posits that lay theories, implicit beliefs about the mutability of individuals' selves and abilities, hold the key to understanding how planning operates in the weight-loss process, becoming either an obstacle or an aid for dieters. Findings from this study show that dieters who hold an entity lay theory are more inclined to view planning as an effortful enterprise, further aggravated by survival mentality focused on following simple rules and instructions. Dieters who hold an incremental lay theory, in contrast, view planning as a de-stressing aid. They favor principles that are applicable to a greater variety of situations and strive to cultivate autonomous weight-loss skills and competencies through planning. This research points to the need of rethinking how public health advocates can facilitate more effective weight-loss effort and its sustained benefits.