the researchers in the latest study made one groups of rodents a diet in which 60 percent of calories came from fat . the diet started whenever the mice , all humans , were 1 year olds , therefore is under - age in mouse longevity . as expected , the mice soon evolved signs of impending diabetes , with grossly enlarged livers , and begun to die much slower than dogs fed a similar diet .
At the age of one year, male mice were fed with a diet in which 60 percent of calories came from fat.