The beds were creaking at the Los Angeles airport Marriott last week - and not just for the usual reasons. The hotel was hosting the annual convention of the NAAFA, the National Association to Advance Fat Acceptance, an organisation that self-consciously styles itself as a civil rights movement for fat people, just as the NAACP fights for the rights of African Americans. Fat is the new black. And they came to the city of the skinny to prove it.
But a thousand miles up the coast, the Seattle school board simultaneously took a decision that may come to be seen as a turning point in the struggle against obesity. The board renewed a contract with Coca-Cola to supply vending machines to its schools, but insisted that the machines selling soft drinks can be turned on only after school hours. Other boards are expected to follow suit; some are planning to ban soft drinks from their schools altogether. The food and drink corporates are starting to fret.
In the UK, the obesity pandemic is being handled more quietly. While the NAAFA marches on Capitol Hill and sings a "glad to be fat" song, we have established a Commons health select committee inquiry. But the politics of obesity is stirring here, too. And not just because summer brings out the flesh and its attendant anxieties: although the UK is still some way behind the US, obesity is rising faster in this country than anywhere else in the developed world.
"Obesity is going to be one of the biggest, if not the single biggest issue facing the NHS for the foreseeable future," says Professor Andrew Prentice, professor of international nutrition at the London School of Hygiene and Tropical Medicine.
One in ten British six-year-olds and one in six 15-year-olds are now classed as obese. Among adults, one in five is obese and more than half are overweight. The Palace of Westminster is not immune. A dozen gravitationally challenged Labour MPs are reported to be on the Atkins diet, fearing that their chances of promotion are dented by their girth.
Given the scale, escalation and implications of the problem - obesity shaves a decade off life expectancy, triples the risk of diabetes and heart disease, and costs the NHS half a billion pounds a year - the response from the government has been muted. Actually, to describe it as muted is wildly flattering; the truth is that on this issue the government appears clueless, powerless and entirely lacking in conviction. The occasional small initiative to encourage us to eat five pieces of fruit and vegetable each day is all that is forthcoming: fiddling while Rome fattens.
"Politicians mostly seem to have their heads in the sand about this," says Dr Susan Jebb, from the Medical Research Council's Resource Centre for Human Nutrition Research in Cambridge. She and other experts giving evidence to the health select committee in July were unanimous in asking for bolder state action.
Prentice, who says he has become more convinced of the case for intervention, draws a historical parallel: "In the past, many public health issues, for example around infectious diseases, have been dealt with in determined, even harsh, ways by governments or local authorities acting with a benign, paternalist mindset."
Most of the experts believe the timidity of the government is the result of the power of the food industry lobby, which is certainly considerable. The Food and Drink Federation is one of the heavyweights of the corporate lobbying world. "I've seen how this lobby works and it is awesome," says Prentice. "For new Labour, which is so anxious to be the friend of business, it has proven too strong, at least to date."
But the political difficulties with obesity go deeper than the fear of waging war against Big Food. When the Labour Party floated the idea of withholding some medical treatments from patients who refuse to give up smoking or lose weight, it was the anti-fat portion that created controversy. There are three fundamental difficulties with constructing a sensible anti-obesity politics.
First, obesity has no single cause and thus no single solution. An anti-smoking campaign has a fairly clear target. But obesity is caused by a mixture of the overconsumption of food, or of certain foods, changing work patterns, TV, travel choices, technological advances (such as the PC) and insufficient exercise. Advertising and the media also play their part, simultaneously promoting the foods that make us fat, the skinny body image to which we should aspire, and the diets and diet products supposedly to close the growing gap between the two.
Long-running expert arguments about whether the primary cause is sloth or gluttony have ended in broad agreement that both sides of the equation are important. Although the figures are disputed, it looks as if a typical Brit now consumes at least 250 calories more per day than two decades ago - the energy equivalent of a four-kilometre run.
In addition, we are eating more than we admit to. Self-report surveys suggest we each eat 82 grams of chocolate per week. But the confectionery industry sells 250 grams per person per week, so a lot of us are lying. The UK is in the bottom quarter of EU countries for the proportion of people doing at least moderate exercise for 150 minutes per week; and we cycle just four billion miles a year, compared to 23 billion in the 1950s.
A policy to tackle obesity is not simply about changing the way we eat, or work, or travel, or exercise - it is about changing the way we live. "One of the difficulties I have when talking to politicians is that I can't demonstrate one thing that makes a difference," says Jebb. "I can't say 'if you do this, that will happen', and that's what ministers want."
And this means that it is far from clear where, within government, responsibility for obesity lies. The Department of Health obviously has an interest; but the Food Standards Agency also has a vital role; as does the Department for Culture, Media and Sport - and at least as much in the "M" section dealing with advertising as the "S" section promoting exercise. But a concerted attack on obesity would require fiscal intervention, too, discouraging energy-dense food consumption and encouraging more active lifestyles. So Gordon Brown would also need to be at the party. Obesity is the most urgent example of a policy area in need of "joined-up thinking" - and we all know how far that idea got.
A second obstacle for politicians is the fear of stigmatising overweight people. It is difficult to construct a message that is emphatically against weight gain without being against weighty people. The task is made harder when rates of obesity are much higher at the bottom than at the top of the socio-economic scale. For many, the thought of slim, middle-class, Labour politicians lecturing the overweight poor is too horrifying to contemplate.
Even the experts are mixed up about stigma.
"It is useful in terms of persuading people not to gain weight, but there is no point in making people who are already overweight feel bad about it," argues Jebb. "I must admit I am in a real quandary about this issue."
The fear of causing offence is now becoming a serious obstacle to combating obesity. Few hesitate to say that smoking is bad and stupid; but being obese has similar health effects. Indeed, the stigma against being overweight may be one of the few forces that has worked against the rising tide of obesity. The danger is that, as being overweight becomes the norm, and being obese unexceptional, even this check will be lost. In the US, the stigma attached to being very overweight has lessened considerably as average weights have gone up. Prentice cites research showing that, in the 1970s, being obese was a less desirable characteristic in a potential marriage partner than a criminal conviction for rape; nowadays it is only a relatively mild negative.
The difficult political trick is to send a clear message that there is collective responsibility for the factors leading to weight gain, as well as an individual responsibility for good health. There is certainly no groundswell from the public for tougher action. Most people think weight is an individual concern, not a government issue. A recent (unpublished) paper from the Cabinet Office floated various measures to tackle the crisis, but concluded that there was no "moral consensus" in favour of intervention. Politicians are waiting for the population to care.
This line of thinking infuriates many in the field. "It comes down to whether the government wants to lead or follow," says Jebb. "I think it has a moral responsibility to take a clear leadership decision to try and turn this public health juggernaut around. It is the job of governments to consider the evidence, look at the trends and take decisions on our behalf. Joe Bloggs does not know the research, the data: he relies on the government to set the agenda."
And there is plenty that ministers could do. Better labelling of products, especially those sold in fast-food restaurants; taxes on energy- dense foods (the mayor of New York, Michael Bloomberg, is considering a 1 per cent tax on ice cream and fizzy drinks); advertising campaigns for healthier lifestyles; better-quality school meals; a ban on advertising food and drink to children; subsidies for gym membership and sporting activities. Most have been tried in at least one country, and in a few - Finland being a dramatic example - the trend towards sedentary lifestyles and expanding waistlines has been halted or reversed.
But underlying the arguments about corporate power, cross-departmental responsibility and stigma is a third and more profound challenge to the development of policies to combat obesity. It is the liberal argument that the state has no right to interfere with choices freely made by individuals and which have negative consequences only for those individuals. As every undergraduate philosopher knows, what J S Mill called "self-regarding" actions do not fall within the orbit of government.
Roy Hattersley, writing in the Guardian, colourfully drew this distinction with regard to food and smoke: "I am a stone overweight and addicted to Burgundy and chocolate. But, foolish though I undoubtedly am, I encompass only my own destruction. I do not go into restaurants and force the family at the next table to share my Flake. Nor do I pour cheap wine down the unwilling throats of people who sit next to me in theatres. Yet smokers insist I inhale their tobacco fumes."
The real breakthrough in the argument over restrictions on smoking, for example in workplaces or public places, came with the production of compelling evidence for the harmful effects of passive smoking. My freedom to smoke has to be balanced by your freedom to breathe smoke-free air. But my obesity does not increase your risk of diabetes or heart disease. Where, then, are the grounds for the state to intervene?
The liberal justification for interference tends to rely on fiscal arguments, such as the fact that the NHS now spends more on obesity-related conditions than on smoking-related ones in Scotland. As Prentice says: "If you are obese, you are, as a result, taking a grossly higher portion of the resources of the NHS, which is funded out of my taxes, too." But this argument does not really stand up to proper interrogation, as even the good professor realises: following our interview, he was off for a paragliding lesson. Ought my taxes to pay for his treatment if he should break his neck as a result of choosing such an absurdly risky pastime? Or how about the 400 people who intentionally harm themselves each day? Once the principle of universal care, free at the point of delivery, is lost, all kinds of exclusions might come to be applied, depending on the prejudices of whichever administration happened to be in office.
The only occasion when my girth has a direct impact on you is in a situation of restricted space, such as an airline seat. So Barbara Hewson received a £13,000 payment from Virgin Atlantic after being squashed by an obese fellow traveller and suffering a haematoma in her chest, torn leg muscles and sciatica. Perhaps her neighbour had read the "travel tip" offered to oversized passengers by the conventioneers in LA: "When you get to your seat during pre-boarding, raise the armrest between seats. This may give you the inch or two of extra space you need. The chances are that the passenger who will be seated next to you won't say anything; if he does, smile pleasantly and say that you'll both be more comfortable if the armrest is up." Thus do two of the most visible liberties of late capitalism - the freedom to fly and the freedom to be fat - collide.
But for the most part such collisions are rare, and the argument of harm to others is pretty weak. The stronger case for intervention is that the choices people make which lead them to be overweight or obese are not free ones at all. As Tim Lobstein, director of the Food Commission, pointed out to the Commons select committee: for every pound the Health Education Authority spends promoting healthy diets, £800 is spent by the food industry encouraging us to eat their products. "Of those products, about 95 per cent are ones that would have encouraged weight gain rather than a healthy diet."
Lobstein believes that the bombardment of advertising and the ready availability of cheap, energy-dense foods have created an "obesogenic environment, a toxic environment that is encouraging obesity all the time. Particularly for children, it is almost impossible to expect them to swim upstream against the flood of stimuli that is sending them rapidly downstream." Children see ten food or drink adverts during each hour of television.
The trend towards super-sizing of portions in fast-food restaurants, and of chocolate bars, is seen as particularly damaging. All the evidence is that people are just as hungry an hour after eating a Chunky Kit Kat as they are after a normal Kit Kat; so the calories are simply added on to the daily intake. But, the experts say, this choice - which the firms encourage through their pricing strategies - is not a truly free or informed one. Consumers cannot be expected to understand that their body's chemistry, designed to respond to hunger, is hopeless at recognising satiety.
Prentice argues that the idea people are making free choices is a fiction promoted by the industry to justify its failure to take responsibility. "I think there is a good chance that litigation against the fast-food companies will ultimately be successful," he says. "People trained in a Pavlovian way to love the Golden Arches are not making free choices. It is entraining attitudes, from Ronald McDonald onwards."
On the other side of the argument, the food and drink companies insist on consumer sovereignty. A bill heading for the US Congress which protects food and drink companies from litigation tells its story in its name - the Personal Responsibility in Food Consumption Act. John Sutherland, from Cadbury - which created a storm with its Get Active (or Eat a Mountain of Chocolate to Get One Volleyball for Your School) campaign - says: "I think litigation is extremely unlikely. At the end of the day, people exercise free will and choice in terms of what they eat."
These are treacherous political waters for any government. The only clear example in the UK of legislation to stop people doing things that are bad principally only for themselves are the seat-belt laws (to which the paternalist obesity experts therefore refer constantly). And even these were fairly controversial, notwithstanding the absence of a powerful industrial lobby with everything to lose.
Perhaps pressure will come from the consumers, courts and the financial markets. JP Morgan has recently warned investors that the share prices of big food companies are vulnerable to the likely wave of litigation. Kraft has just broken ranks, cutting portion sizes, fat levels and marketing to children. The significance of this move was not in the specifics of the changes, some of which are of doubtful value, but that Kraft has explicitly recognised that food companies have a share of the responsibility for the rise in obesity.
But without decisive, concerted and confident government action on a range of fronts, none of these seems likely to stop a trend that will make obesity the rule rather than the exception within a matter of decades. It is hard to see many immediate political upsides - but lots of danger - for anyone who takes this issue on. But I am pretty sure I've heard our Prime Minister say that politics is about making tough choices. The leaders of the US and the UK have proved willing to pursue other struggles in the face of opposition. Will the seven-minute miler Bush and the treadmill-pounding Blair have the guts to fight the battle of the bulge?