Roger Bingham takes viewers to the Pima Indian Reservation in Arizona. Obesity runs rampant among the Pimas, resulting in an epidemic of diabetes and hypertension. Their weight problem can be linked in part to what scientists call a "thrifty gene," which during ancient times enabled the Pimas to store fat when food was in short supply.

FAT CITY also investigates other genetic and environmental factors that may account for expanding waistlines, including metabolic rate, diet, exercise, and the brain's biochemistry. Bingham discusses the controversial "set point theory" of weight regulation, an internal mechanism that seems to keep weight within a fairly constant range.