ABSTRACT
Insulin resistance develops commonly during middle age in the rhesus monkey, in association with the gradual progressive development of obesity. Most monkeys who are demonstrably insulin resistant and obese (body fat 25%) subsequently go on to develop overt type 2 diabetes. These conditions are naturally occurring and become evident even as the monkeys are maintained on a “healthy heart diet” consisting of laboratory chow high in fiber and low in fat with near zero cholesterol. Insulin resistance and obesity develop in both free ranging monkeys, and in individually housed monkeys. In the free ranging monkey, the environmental conditions must provide protection from predators, minimization of exposure to diseases, and most importantly, the diet must be provided so as to permit ad libitum feeding. Some factors contribute to disease development in aging free ranging or laboratory animals, and other factors may prevent the development of obesity and diabetes. Our work with laboratory maintained monkeys has shown that calorie restriction (CR) at levels which maintain body fat between 17% and 22% is sufficient to prevent the development of these diseases (Hansen and Bodkin, 1993).
