On a break from fighting crimes and handling traffic jams, pot-bellied policemen in Bangkok are combating another enemy: obesity.

An effort is under way to whip Thailand's overweight officers into shape during a 12-day bootcamp.

About 60 overweight officers from around the country are taking part in the programme, which includes dawn-to-dusk exercise and lectures on healthy living at a police training centre in suburban Bangkok.

Wearing T-shirts with the slogan "Get rid of the belly," they start their days with pre-dawn jogs followed by yoga, aerobic dance classes, tai chi to reduce stress and improve blood flow, and lectures from nutritionists and trainers.

The biggest weight loser at the end of the scheme will win 5,000 Thai baht - a bonus for underpaid police officers, though many say their real motivation is the chance to improve their health.

"The school children call me 'Uncle Fat' all the time, but I don't mind. I'm more concerned about my health, because I have diabetes," said Sgt Maj Wanchat Phonorthong, a 49-year-old traffic officer who weighs in at 20st and is 6ft tall.

"I'm going to lose some of my belly because they have me work out every day and they only give me half the food I usually eat. It's torture, but I have to do it for myself," he said.

Annual check-ups last year for Thailand's 200,000 police officers showed that the five most common concerns were obesity, high cholesterol, liver problems, high blood pressure and diabetes.

Colonel Pornpen Bunnag, who designed the course and heads the family medicine department at Bangkok's Police General Hospital, said: "Police officers tend to have higher health risks than some other professions because they don't eat and sleep on a normal schedule. Eating at the end of late-night shifts, drinking and smoking all contribute to their obesity."

She added: "Not only that - their pot bellies make them look less sharp in their uniforms."