consuming an extra 2,000 calories per day, far more than was theoretically neces- sary. Evidence suggests that a metabolic speed-up is triggered after two weeks of overeating or a cumulative 20,000-calorie surplus.
The body also regulates eating. In an experiment run by University of Pennsylvania psychologist Theresa Spiegel, volunteers subsisted on a milkshake-style beverage dispensed from a reservoir they could not see. They soon began drinking just enough to get about 3,000 calories daily-the...