Problems associated with excess bodyweight and obesity are increasing worldwide. These problems increase risks of metabolic syndrome, cardiovascular disorders and hypertension. Improving diet and exercise control and self-monitoring, self-evaluating and self-adjusting are critical to modify risky lifestyles. In this paper, the author's designed a diet control protocol and then applied it to an obese adult. The project ran from Feb 2nd to July 30th, 2009, and used the principles and concepts of self-regulation theory, a daily diet plan, and body weight chart to guide the patient to consider and appreciate the gaps between his behavior and the standard in order to encourage improvement. The processes related to the goal and effect are significant. By learning self-regulation skills the patient’s weight declined from 106.1 kg to 84.4 kg. Self-efficacy also improved. The author predict the efficacy of the approach in helping prevent chronic disease. The author wishes to share their experience with nursing colleagues and propose this protocol as an effective diet control approach for obese patients.