Since 2008, health checkups and guidance for insured persons aged 40 to 74 aim to reduce lifestyle related disease risks. This study compares weight changes from same day versus later health guidance focused on exercise or diet. Participants in 2023 received either same-day or later health guidance, targeting energy reduction through exercise or diet. Ethical approval was secured, and data were stored securely. Of 185 participants, 113 received same-day guidance and 72 later. Average weight loss was 0.12 kg same-day and 0.31 kg later. Diet-focused guidance yielded -0.21 kg same-day and 0.49 kg later; exercise-focused guidance showed 1.71 kg later and -0.3 kg same-day. Both guidance timings led to weight loss, with diet-focused same-day and exercise-focused later guidance being most effective. Time constraints limited same-day exercise guidance efficacy, favoring diet advice, while later sessions better facilitated lasting exercise behavior changes.