Answer to Question 1
In effect, people who gain or lose weight will experience metabolic changes that strive to bring the body back to its natural weight. If fat levels decrease below our body's normal range, the brain (specifically, the hypothalamus) compensates by slowing metabolism. We begin to feel lethargic, we increase our sleep, and our body temperature decreases slightly to conserve energy (which is why many persons with anorexia complain of being cold). In this state of relative deprivation, uncontrollable urges to binge are common because our bodies are telling us that they need more food than they are getting to function properly. Similarly, the body fights against weight gain by increasing metabolism and raising body temperature in an effort to burn off extra calories. (Admittedly, this valiant effort is seldom enough to conquer the force of holidays and other feasts.) Because of its responsivity to change, researchers often compare the body's setpoint to the setting on a thermostat that regulates room temperature. When room temperature falls below a certain range, the thermostat automatically sends a signal to the heating system to increase the heat level until it again reaches the established temperature setting. Human bodies respond similarly to deviations in body weight by turning their metabolic furnace up or down (Wilkin, 2010).
Answer to Question 2
Decreasing caloric intake reduces a person's metabolic rate, which allows fat to remain in the cells so that weight loss is, in fact, impeded. This failure to lose weight sets the stage for a vicious cycle of increased commitment to dieting and vulnerability to binge eating.
Psychological consequences also contribute to this cycle by creating what some researchers call the false hope syndromean initial commitment to change one's appearance leads to short-term improvements in mood and self-image, but this hope declines as feelings of failure and loss of control increase (Polivy & Herman, 2005). Loss of control may lead to binge eating, and purging is seen as a way to counteract the perceived effects of binge eating on weight gain.