When your body weight changes, this causes a change in the performance of the energy it has. That creates a fear of weight regain after dieting. This process is very easy to explain; because the increase in food consumption leads to increased fat mass, lean mass and weight body, if you increase the weight of the individual, the minimum energy requirements of the body to keep you also increase, representing a limit weight gain.
Conversely, if you develop a routine physical effort, the minimum energy consumption increases due to energy represents the exercise. Therefore, if ingested an equal amount of food without doing any exercise (assuming that the individual will be in a stable weight regardless of value), then the body will burn up power represented by fat in the body and thus reduce its weight.
Any reduction of energy inputs, decreases fat mass and lean mass after causing decreased thinning curve just stabilized even in the case of very low energy inputs. This energy balance is a problem for those people who start a regular physical activity and increase the amount of food they consume.
At the time they leave the continuity in the exercise, then inevitably incur a weight gain because normally keep the volume of food.
Usually this is seen in people who start a fixed calorie diet and physical activity that accompanies it. Reached the target weight loss, many people abandon the diet and/or exercise. Having reduced their weight, minimum energy consumption will also be reduced, so that they should not return to an unlimited supply, but look how many calories they eat.
In the case of having achieved the goal of reducing weight and leave the physical activity, then they will reduce their daily energy consumption and therefore gain weight again if not caring how much energy they consume.