Body weight and longevity in genetically obese and non-obese mice fed fat-modified diets.

Polygenically obese and genetically related non-obese male mice were fed ad libitum purified diets differing in quantity or type of fat from weaning onward to determine effects upon weight gain and life span. Non-obese mice lived 71% longer than mice in the obese line (mean = 753 d versus 441 d). Obese mice fed a low-fat diet containing 1% corn oil by weight lived 26% longer than their obese counterparts fed high fat diets containing 20% additional fat as either corn oil or beef tallow. The low fat diet had more of a normalizing effect upon longevity than upon body weight in polygenically obese mice. Conversely, dietary fat concentration had little effect upon longevity in non-obese mice and more effect upon body weight than in genetically obese mice. Type of dietary fat had little effect upon body weight and no effect upon longevity. The results of this study suggest that life span was only partially explained by body weight, and furthermore, that genetics play a greater role than body weight or dietary fat concentration in determining life span.