the experiments in the earliest study fed one group of men a diet in which 60 percentage of calorie came from fat . the starvation started because the mice , all female , were 1 season old , which is middle - age in male longevity . as expected , the mice shortly developed signs of impending diabetes , with grossly enlarged livers , and continued to die much sooner than mice fed a standard diet .
At the age of one year, male mice were fed with a diet in which 60 percent of calories came from fat.