Image caption Would a $50 penalty help change lifestyles?

Overweight welfare claimants in the US state of Arizona face paying $50 (£31) fines if they don't follow a dietary regime laid down by their doctor. Is that fair?

Just as American waistlines - like many in the Western world - continue to expand, so does the budget to meet the associated costs.

Medicaid, the programme which provides healthcare for the poor, costs the US federal and state governments $339bn (£209bn) a year, a figure climbing 8% annually.

The federal government matches state spending on the program, providing as much as $3 for every $1 spent in poorer areas.

Given the size of the budget, it's no surprise that Medicaid has become one of the fiscal battlegrounds in Congress.

Why the Medicaid bill is rising Medicaid is the state health programme for people on low incomes

In recession, more jobs are lost, incomes decline and people lose employer health cover

This results in higher Medicaid enrolment

At the same time, state revenues are declining

Medicaid enrolment has increased by 6m people in last few years

Not to be confused with Medicare, which is the state health insurance cover for over-65s Source: Kaiser Commission

President Obama's healthcare reforms would extend cover further, increasing costs to states by tens of billions of dollars. But the Republican budget proposal put forward by Congressman Paul Ryan caps the government contribution, saving an estimated $750bn (£463bn) over 10 years, but forcing states to make cuts.

Now the state of Arizona is proposing a radical idea. It wants to impose a $50 annual fine for overweight Medicaid recipients who don't follow a strict health regime developed with their doctor. Those with children, and people overweight due to a medical condition, would be exempt.

Smokers and diabetics who ignore their medical advice would also have to pay.

Monica Coury, assistant director at Arizona's Medicaid programme, says the aim is to change behaviour using a carrot and stick approach, in the same way that increasing cigarette taxes reduced smoking.

"It's undeniable that there is a link between obesity and the rising cost of healthcare in America, so we can't be afraid to discuss this issue.

"It's reaching a crisis level in the US and we continue to complain about the rising uncontrolled costs of care - and yet we don't drill down and test some of these concepts."

Would a fine encourage weight loss? "It's a silly idea. Overweight people are motivated to lose weight but it's very hard. Only 5% of people lose weight and keep it off for five years. The state would be wiser to change the conditions driving obesity rather than penalising people that have it." Kelly Brownell, Rudd Center for Food Policy and Obesity, Yale University "The reason people are obese is complicated and saying 'eat less' is not enough. People don't have access to grocery stores that carry healthy foods, don't have the funds to buy them and don't have the education to know what to buy." Ziporah Janowski, Camp Shane weight loss camp, Arizona

Rewards for those who meet slimming targets could come in the form of keep-fit videos or other kinds of incentives, says Ms Coury. People with children, and those overweight due to a medical condition will not have to pay.

"But if you are just an average person who is able to do something to address your weight issue, and your doctor believes you can do something about it and prescribes a regime for you and you choose not to follow it, your treatment [for heart problems in later life, for example] is costing more and we're asking you to put something back to the system."

Details of how the scheme, put forward by Governor Jan Brewer, would be administered have yet to be thrashed out, and would be agreed if the state gets the go-ahead from Congress.

Although some private companies have similar penalties in their health insurance cover, this would be the first time any state health care programme has charged people in this way for what could be deemed an unhealthy lifestyle.

If your wife is nagging at you, you roll your eyes and eat another chip, but if your doctor says you have to lose 10lbs, then you take it more seriously Fitness instructor Lisa Johnson

Arizona has the second-highest proportion of Medicaid recipients in the US, and a quarter of its residents are classed as obese. Among its other plans to cut its annual $10bn (£6.2bn) Medicaid bill is to freeze enrolment for some childless adults.

Other states will be watching closely as they all scramble to cut costs, says Matt Salo of the National Association of Medicaid Directors.

"They don't know how they will survive the next two years. States are facing a $175bn (£108bn) shortfall. It's a huge amount of money and it's a time of great uncertainty.

"What Arizona is doing is a combination of short-term budget savings that will have a long-term change of behaviour with health outcomes.

"Is this the answer? I don't know, but people are looking at it closely because there are so few other options."

Some overweight people believe it could work. Kevin Woodman, 46, weighs 264lbs (120kg) and lives in Tucson, Arizona. He lost 161lbs (73kg) in nine months by cutting out carbohydrates and enduring a strict fitness regime at a boot camp called Swat.

"A friend offered me $1,000 to lose weight and I didn't, I gained weight," says the radio show host. "For me, it was only when I was faced with losing a limb or diabetes that I lost weight. But for those on low incomes, this could work."

But Arizona Senator Kyrsten Sinema thinks the tax is unfair because people like her diabetic grandmother could be penalised because there is no system to determine when a person is or isn't following a medical regime.

Ballooning budgets and waistlines Michelle Obama (above) has led an anti-obesity campaign called Let's Move

For every dollar spent on health care, 83 cents is spent on a patient who is overweight or obese

Annual health costs related to obesity in the US are as high as $168bn (£104bn)

25.5% of Arizona residents are obese, which is about the US average Source: Campaign to End Obesity

Most Americans would agree it's not fair for healthy people to subsidise unhealthy people, she says, but unhealthy people who work for the state and get state health insurance aren't subject to this proposal.

"This proposal targets only the working poor and elderly, and includes punishing people like my grandmother who aren't unhealthy but have a medical condition."

A better solution to spiralling Medicaid costs, she says, is to lift more people out of poverty by creating jobs in the state.

This is just another example of nanny-state social engineering, says Wes Benedict of the Libertarian Party.

"If you want to save the state money, which libertarians do, cut Medicaid across the board, but don't single out overweight people and smokers. I wouldn't be surprised if this programme costs 10 times more to administer than it saves."

The $50 fine alone might not be enough to change behaviour, says fitness expert Lisa Johnson, but it could help encourage doctors to talk about weight issues with patients.

"A recent Harvard study said 61% don't have time to talk to patients about weight loss, so this could have a more dramatic impact on the way doctors see their patients than on the behaviour itself.

"If your wife is nagging at you, you roll your eyes and eat another chip, but if your doctor says you have to lose 10lbs, then you take it more seriously."