Fat as insurance, leanness as bodily display: did Ronald Reagan make us fat?

Standard recommendations to reduce body fat (eat less and exercise more) have been largely unsuccessful at achieving sustained weight loss. Bodies have evolved to deposit fat as insurance against future food shortage. Given sufficient energy income, the amount of fat carried by a body is a physiological choice because thermogenic mechanisms allow the body to dump excess calories to the environment as heat. Bodies evolved to maintain a level of fat that balanced the current costs of carrying fat against the bodily-perceived risk of famine. Intense physical activity favors less fat to lighten the load being carried. Dieting may be ineffective in achieving sustained reductions in fat mass because it causes reductions in thermogenic energy expenditure to protect fat reserves and because it communicates to the body that it had been underinsured, favoring deposition of additional fat once diets relax. Recent increases in body weight hint that bodies perceive the current environment as one with greater need for fat as insurance. Increased economic insecurity associated with recent economic changes may have been interpreted by ancient bodily mechanisms as a reason to store additional fat.