For many people, being overweight or obese primarily results from a combination of
excess calorie consumption and/or inadequate physical activity.
Body fat historically enabled people and animals to survive food shortages by tapping
into their internal energy reserves. Today, abundant calorie-rich food often overwhelms the
body’s weight regulatory system, with many individuals’ genetic makeup unable to control this
input, resulting in massive societal weight gains. The current era of obesity and inactivity is
threatening the substantial progress made in postponing illness and death and with its reduction
in cardiovascular disease made possible in part because of a decrease in smoking.