decrease) in energy expenditure may be driven by an increase (or decrease) in fat or lean mass without regard to a fixed set weigh or fat level and without active regulation to offset the increased (or decreased) consumption. However, the return to normal weight after subjects have their caloric intake strictly limited happens faster than would be expected in a model without active regulation (i.e. subjects return to normal weight faster than if they simply returned to normal eating habits. Another alternative is the dual intervention point model. The dual intervention point model posits that rather than a body weight set point, there is a set range for body weight. Under this model, active compensation happens only outside of upper and lower intervention points, while for weights within the set range environmental factors would have a strong effect on body weight since there would only be passive compensation for changes in weight. Differences in propensity for obesity between individuals would then be explained as individuals prone to obesity having a wide set range that extends into higher weights. In the dual intervention model, the lower and upper limits of the range are independently set, with the lower end of the range set by evolutionary pressure due to the risk of starvation if too much weight is lost and the upper bound set by pressure due to increased risk of predation if too much weight is gained. See also Setpoint (control system) for the general concept as it applies to control systems in general. References Human body weight Weight loss Obesity