OSAKA (Kyodo) Overweight rhesus monkeys in Sakai, Osaka Prefecture, have managed to shed their excess weight thanks to a strict diet regimen over the past two years.

Some of the Ohama Park monkeys were so fat their protruding bellies dragged along the ground. They were even dubbed "metabo-zaru," or metabolic syndrome monkeys, after their overweight human counterparts.

Park officials believe the monkeys packed on the extra kilograms largely because of snacks visitors threw at them.

More than 30 percent of the troupe of about 50 monkeys were considered obese and weighed more than 10 kg in 2007.

The heaviest of all the creatures — a male — tipped the scales at 30 kg.

Starting in June 2007, park officials took matters in hand and put the primates on a strict diet. As a result, all but 10 of the overweight monkeys slimmed down to less than 10 kg.

Even the heaviest managed to trim down to 17 kg, although his skin is now wrinkly and sags.

To keep the monkeys away from the tempting snacks, the park has built a new pen with metal screens that make it impossible for visitors to feed them.

"We want them to shape up further in the future by having them exercise," said Masashi Kyotani, head of the park office.