Leah Nash for The New York Times
Shiva weighs twice the norm. More Photos »
Leah Nash for The New York Times
At 45 pounds, Shiva is twice his normal weight and carries much of it in his belly. He can eat all the pellets he wants and snack on peanut butter, but gets barely any exercise. More Photos »
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.
“Nonhuman primates don’t lie to you,” said Dr. Grove, who is a neuroscientist. “We know exactly how much they are eating.”
To allow monitoring of their food intake, some of the obese monkeys are kept in individual cages for months or years, which also limits their exercise. That is in contrast to most of the monkeys here who live in group indoor/outdoor cages with swings and things to climb on.
While this research is not entirely new and has been the target of some animal rights’ group complaints, demand for the overweight primates is growing as part of the battle against the nation’s obesity epidemic, according to Dr. Grove and other researchers working with such monkeys in Florida, Texas and North Carolina, and also overseas.
Some tests have already produced tangible results. Rhythm Pharmaceuticals, a start-up company in Boston, tested its experimental diet drug on some of the Oregon monkeys. After eight weeks, the animals reduced their food intake 40 percent and lost 13 percent of their weight, without apparent heart problems.
“We could get a much better readout on chronic safety and efficacy early,” said Bart Henderson, the president of Rhythm, which now plans to move into human testing.
In another study, a group of academic researchers is using the monkeys to compare gastric bypass surgery with weight loss from forced dieting. One goal is to try to figure out the hormonal mechanisms by which the surgery can quickly resolve diabetes, so that drugs might one day be developed to have the same effect. To that end, the study will do what cannot be done with people — kill some of the monkeys to examine their brains and pancreases.
The primate center here, which is part of Oregon Health and Science University, has more than 4,000 monkeys, mostly rhesus macaques. About 150 of them are the rotund rhesuses. Some receive daily insulin shots to treat diabetes, and some have clogged arteries. One monkey died of a heart attack a few years ago at a fairly young age.
Shiva, a young adult, gained about 15 pounds in six months and weighs about 45 pounds, twice the normal weight for his age. Like other monkeys with a weight problem, he carries much of the excess in his belly, not his arms and legs.
The monkey’s daily diet consists of dried chow pellets, with about one-third of the calories coming from fat, similar to a typical American diet, Dr. Grove said, though the diet also contains adequate protein and nutrients.
They can eat as many pellets as they want. They also snack daily on a 300-calorie chunk of peanut butter, and are sometimes treated to popcorn or peanuts. Gummy bears were abandoned because they stuck to the monkeys’ teeth.
