The purpose of computing is insight, not numbers.
--Richard W. Hamming, 1962
The rubber bag explains the mechanics gaining and losing weight. But why can some people control their weight effortlessly while others seem locked in a lifelong struggle against obesity? To understand this and find a path to permanent weight control, we must again step back from the daunting complexity of the human body and seek enlightenment from a much simpler model. Consider how a thermostat controls the temperature.