All those who believed they could shed the extra few pounds by diet alone, they were sadly mistaken...
Food is not always plentiful for humans and animals and the body seems to have developed a strategy for responding to these fluctuations.For example when the caloric intake is less, animals tend to reduce their activity levels.
Monkeys were studied. The monkeys were placed on a high-fat diet for several years. They were then returned to a lower-fat diet There was no weight loss at the end of a month.
However naturally occurring levels of physical activity for the animals began to diminish soon after the reduced-calorie diet began.
A comparison group of three monkeys fed a normal monkey diet and was trained to exercise for one hour daily. This group did lose weight.