An experimental drug has helped monkeys lose about 11 per cent of their body weight, researchers have found.

The drug starves the blood supply of fat cells.

The approach differs from previous efforts to cure obesity through drugs. Those focused on medications that suppress appetite or increase metabolism. But side-effects have limited their appeal.

Cancer researcher Dr. Wadih Arap of the University of Texas M.D. Anderson Cancer Center and his colleagues are investigating obesity because of its link to cancer.

"Obesity is not only a major risk factor for many, many cancers, prostate, breast and ovarian," said Arap. "But it's also a prognostic factor. Obese people do worse, they do worse with chemotherapy and surgery and some radiation therapies."

The researchers are testing a synthetic molecule that works on fat cells. After initial tests worked on mice, Arap found new research subjects: rhesus monkeys with the habits of couch potatoes.

"They choose not to exercise and they choose to overeat, so in the same conditions of the other monkeys they become overweight all on their own," veterinary researcher Dr. Kirsten Barnhart said of the flabby, inactive primates that seem to just sit and stare at their food trays.

In contrast, the other monkeys in the colony show more typical active behaviour, flinging themselves around the cages.The monkeys regained weight when the drug injections stopped, says Dr. Kirsten Barnhart. (Courtesy of Dr. Wadih Arap)

After 28 days with the experimental drug, the obese monkeys lost weight, despite eating the same amount of food as usual and remaining inactive.

The researchers used MRI to gauge abdominal body fat, which is thought to be the most dangerous area for humans to gain weight because it raises the risk of developing Type 2 diabetes. The abdominal fat in the treated monkeys was reduced.

Barnhart believes the drug shows promise but isn't a magic bullet for fighting obesity. The drawbacks include:

• Daily injections.
• Kidney side-effects.
• When the injections stopped, the fat came back.

Barnhart would like to see the drug developed into a safer pill form for people. She believes it could be effective as a first step to help lose weight, particularly for the morbidly obese.

The drug, called Adipotide, targets white fat — a particularly unhealthy type of fat that accumulates under the skin and around the abdomen — reducing its effects.

Shrinking fat cells

"These [white] fat cells produce a lot of chemicals, and some of these act very much like toxins to wreak havoc in the body," said Dr. David Lau, an obesity specialist at the University of Calgary. He studies the properties of fat cells and says our knowledge of their influence in the body has changed tremendously.

Fat isn't just a sponge full of energy, said Lau. Fat secretes hormones, communicates with the brain to interfere with metabolism and is an active organ with a life of its own, he said.

At his lab, investigators are taking a different approach to fighting obesity. They're hoping to interfere with the signalling mechanisms in order to shrink fat or prevent it from developing in the first place.

That's because scientists now know that "fat begets more fat," Lau said, meaning fat cells have the potential to keep reproducing in the body.

For now, the researchers all stressed the best cure for obesity remains prevention through a healthy lifestyle.

Arap holds a financial stake in drug-development companies.

This week CBC News reports on the search for cures for aging, Type 1 diabetes, the common cold, obesity and cancer on CBC Radio One, CBC News Network, The National and at cbc.ca/news/health/.

With files from CBC's Kelly Crowe and Pauline Dakin