The English city of Manchester has come up with a simple formula it hopes will help keep its citizens trim: eat right, get stuff. Exercise, get more stuff.

Manchester is hoping to fight fat with a reward system that works like a retail loyalty card. But instead of earning credit for opening their wallets, residents will be rewarded for keeping their feet on the treadmill and their fridge stocked with healthy food.

Starting next fall, Manchester residents will be able to swipe their rewards cards and earn points every time they buy fruits and vegetables, use a community swimming pool, attend a medical screening or work out with a personal trainer. Points can be redeemed for athletic equipment, donations to school athletic departments and personal training sessions with local athletes.

The money is coming from the government's health service and from local authorities.

"We're not looking for customers to be loyal to a particular store, but to help people make healthier choices," said Laura Roberts, the chief executive of Manchester's National Health Service.

One public health official said the program seemed worth pursuing even if it is untested.

"I haven't seen any evidence that it works, but that doesn't mean we shouldn't try it," said Timothy Armstrong, coordinator of the World Health Organization's global strategy on diet, physical activity and health. Armstrong said obesity was such a pressing issue that "as public health officials we really don't have the luxury of waiting to see what works and what doesn't."

He said he was particularly impressed that Manchester, which has a population of 2.5 million, had managed to rope grocery stores, advertisers, fitness clubs and private companies into the plan.

"We really do know that, in terms of curbing the obesity epidemic, all of society needs to play a role," he said.

Like other countries in the developed world, Britain is struggling to keep its citizens' waistlines in check. Last year a government-commissioned report predicted that as many as nine out of 10 adults could be overweight by 2050, costing the country's National Heath Service more than $78 billion a year.

Manchester's program is modeled after the kind of reward programs run by major British grocery chains, such as Tesco and Sainsbury's. Manchester, a city of around 2.5 million people

Health officials haven't determined how much effort it will take for people to win rewards, but they won't have to climb a mountain before they can earn something, said Andrew Lawton, one of the developers of the program, called Points4Life.

"Normally, if someone in the private sector was building a program, they would want to see a profit, but we're doing this altruistically, which means we can pass a good value back to the customers and patients," Lawton said.

Armstrong said the rewards program is worth trying, even if it means paying people to do what they should be doing anyway.

"I don't really like the word bribe, but if we can influence people to make the right choices, or healthy choices, we should make every effort to ensure that they do that," Armstrong said.

In Britain, studies have indicated rewards can create good habits where they did not exist before.

At Bangor University in northern Wales, researchers developed a successful program to introduce fruits and vegetables into children's diets. They created young superhero characters called "Food Dudes" and offered kids small prizes if they were willing to try new foods. The program worked so well researchers were gradually able to withdraw the rewards and the good habits stuck.

Though Manchester is the first British city to embrace citizen weight-loss incentives, towns in other countries have tried similar programs. Last year, Varallo, a small town in northern Italy offered cash rewards for residents who lost weight and kept it off for 12 months. Thirty Varallo citizens took up the mayor's challenge.

Rewarding weight loss also has worked for some U.S. companies that want to keep health care costs down. Freedom One Financial Group, based in Clarkston, Mich. sent 21 employees who met weight-loss goals on a four-day Caribbean cruise in 2005.

Manchester is one of nine British communities trying out anti-obesity programs. The city will match the federal government's $7.2 million contribution.

Other places have their own plans. Thetford, about 75 miles north of London, has a project to help people maintain their bikes. In the southern English town of Porsmouth, new signs will help walkers, runners and cyclists time their journeys. Public housing tenants in Halifax, in northern England, are to begin growing their own fruits and vegetables.