HILLSBORO, Ore.  Like many these days, Shiva sits around too much, eating rich, fatty foods and sipping sugary drinks. He has the pot belly to prove it, one that nearly touches the floor  when he’s on all fours, that is.

Shiva belongs to a colony of monkeys who have been fattened up to help scientists study the twin human epidemics of obesity and diabetes. The overweight monkeys also test new drugs aimed at treating those conditions.

“We are trying to induce the couch-potato style,” said Kevin L. Grove, who directs the “obese resource” at the Oregon National Primate Research Center here. “We believe that mimics the health issues we face in the United States today.”

The corpulent primates serve as useful models, experts say, because they resemble humans much more than laboratory rats do, not only physiologically but in some of their feeding habits. They tend to eat when bored, even when they are not really hungry. And unlike human subjects who are notorious for fudging their daily calorie or carbohydrate counts, a caged monkey’s food intake is much easier for researchers to count and control.