Obesity is a major public health challenge. More than one-third of the U.S. adult population is considered obese, a figure that has more than doubled since the mid-1970s. Among children, obesity rates have more than tripled over the same period. Not only is obesity associated with numerous medical complications, but it incurs significant economic cost. At its simplest, obesity is a result of an energy imbalance, with obese (and overweight) people...