April 13, 2011 -- Mario, Hoopa Troopa, Freckles, Casper, Good Lookin', and Cuddlebug and are just some of their names. They are rhesus macaques, monkeys who sit around all day in small cages, snacking on tasty high-fat treats. In fact, sitting and snacking has become their life's purpose.
They are part of a controversial obesity study at the oldest primate research center in the country, the Oregon National Primate Research Center in Portland, Ore., where researchers are trying to turn 150 monkeys into perfect couch potatoes.
The hope is that studying their bodies will provide clues about human obesity, a condition that affects 70 million Americans.
Dr. Kevin Grove, the neuroscientist leading the research, said that the goal here is to mimic the lifestyle and eating habits of obese people.
"We are trying to model that sedentary lifestyle," Grove said. "That sitting around all day eating tasty treats, sitting in the cubicle at work, eating those snacks all day long...they [the monkeys] will sit there and snack, just like a human will."
Kept in small cages to limit exercise, these monkeys are fattened up with high-fat, high-sugar snacks including peanut butter lard treats and a syrupy sugar drink meant to imitate a human's consumption of a can of soda a day.
"They get about 35 percent of their calories from fat," said Grove.
While most of the monkeys don't look obese to the naked eye, there is one that unmistakably does. His name is Shiva, and he weighs 45 pounds, which is more or less equivalent to a 5-foot 10-inch man who weighs 250 pounds.
Shiva's potbelly drags along the floor of his cage when he moves. Much like the other monkeys at the center, he can't seem to hide his excitement when presented with his next treat. The scientific junk food has taken a toll. Shiva is in a pre-diabetic state.
Under these conditions, the monkeys will often develop obesity-related illnesses. In fact, several of them are full-blown diabetics who depend on their daily insulin shots to survive. According to Grove, diabetic monkeys help researchers understand more about how the illness works in humans.
Just as some obese humans can develop heart conditions, researchers said some of the obese monkeys used in the study will die prematurely from heart attacks or cardiovascular conditions.
Critics Respond to Controversial Study
Not surprisingly, using monkeys to study human obesity has provoked some outrage. Kathleen Conlee, the Director of Program Management for Animal Research Issues at the Humane Society of the United States, is among the critics and said she has conducted lab research on the same type of monkey in the past.
"How is this any way mimicking a human condition?" she said of the study. "Humans aren't put in isolation and force fed high calorie diets…This is the kind of thing we consider to be frivolous and unnecessary."
But Dr. Grove insisted studying monkeys under these strict conditions is the best way to make strides in obesity research because these primates are so similar to humans in brain function and behavior.
"They model, they develop the disease in the same pattern as humans do," he said.
He said that while studies on obese humans are critical, they are often difficult for a variety of reasons.
"We simply can't control the environment well enough," Dr. Grove said. "It is also important for us to be able to control all aspects of the environment and the disease. Here we can do that."
Conlee replied that it was a "myth" that monkeys were the best animals to use in studying human behavior.
"We've seen time and again drugs that have failed and had hugely adverse effects on humans, where they relied on monkey testing for the testing of that drug and it gets pulled off the market because of the devastating effects on humans," she said.
Yet Dr. Grove's findings are highly sought after by pharmaceutical companies eager to develop the next obesity drug. The research, funded in large part by the federal government as well as drug companies, has so far yielded some interesting results.
Grove pointed to at least one drug shown to reduce weight and improve glucose control in the monkeys. That drug is expected to be tested soon on humans.
He also discussed other findings he considers important. While studying the offspring of monkeys fed poor, high-fat diets during their pregnancies, Grove discovered that the baby monkeys were more anxious than those who came from mothers who ate healthy diets.
He said this demonstrates how a bad diet during pregnancy "is programming that brain to also seek that high fat diet and those highly palatable diets later in life which are going to make them at higher risk for obesity and diabetes later on."
In response to critics of his work, Grove said they simply don't have a strong understanding about the purpose of his team's research.
"We are not trying to figure out if a high-fat diet makes a monkey fat," he said. "We really need to understand why people, two-thirds of our population, are obese."