Fig. 2.

Biology's influence during obesity development, treatment, and relapse. Homeostatic systems adapt to prevent perpetual weight loss or gain when environmental and behavioral pressures change. The interplay of this balance between the changes in nonhomeostatic pressures and homeostatic adaptations is shown for the initial development and progression of obesity (A–C), during energy-restricted weight loss (D), during weight maintenance after weight loss (E), and during the relapse to obesity (F). Biology may play a more subtle, permissive role during the initial development of obesity, but it becomes a driving force for weight regain after weight loss.