the researchers in the latest study fed one group of mice a diet in consisting 60 pounds of calories derive from protein . the diet started when the mice , all males , were 1 age early , which is middle - stage in mouse ancestry . as expected , the mice soon developed signs of impending insulin , with grossly enlarged livers , and started to die even sooner than mice fed a standardized diet .
At the age of one year, male mice were fed with a diet in which 60 percent of calories came from fat.