An early death with fries, please

You might think it's obvious that fast food makes you fat, if consumed in sufficient quantities, but a new study makes the startling claim that it actually tricks people into overeating. According to Andrew Prentice, professor of international nutrition at the London School of Hygiene and Tropical Medicine, and Susan Jebb of the Medical Research Council Human Nutrition Centre in Cambridge, people who regularly eat burgers, fried chicken and chips are unaware of just how many calories they are consuming: 65 per cent more per bite than standard British meals. Indeed, fast food is so packed with calories that eating an extra 200g twice a week is enough to increase someone's weight by almost 8kg in a year, which may go some way towards explaining why so many overweight people protest, and sincerely believe, that they don't eat much more than their thin friends and relatives.

Previous research has suggested that 21 per cent of British women and 17 per cent of men are obese, and that they are passing bad habits on to their children; some of the most shocking statistics come from the British Medical Journal, which found that a quarter of children under the age of four are overweight and one in 10 is obese. Up until now, discussions on how to combat the problem have tended to focus on getting people to eat more fruit and vegetables and take more exercise, but the latest research turns the spotlight on to the fast-food chains, raising questions about their responsibility to consumers.

So does the controversial suggestion, from a senior public health official, that fast food may be addictive. John Ashton, regional director of public health in the North-west, argued last week that government intervention was needed because "individuals cannot protect themselves from bio-terrorism, epidemics of Sars, the concerted efforts of the junk-food industry, drug dealers and promoters of tobacco and alcohol".

I'm not sure I would mention fast-food outlets in the same breath as someone who sends anthrax spores through the post, but Ashton's argument is another blow to the notion that people are solely to blame for their state of health (or lack of it). As he points out, it is almost impossible at present to discover how much sugar there is in a can of fizzy drink or how much fat there is in a TV dinner, even if people want to know exactly what they are consuming. Prentice and Jebb argue that fast-food chains such as McDonald's, KFC and Burger King should reduce both portion size and the "energy density" - the quantity of calories in relation to weight - of their meals, but I would go further. For years now, tobacco companies have been forced to print warnings on cigarette packets, acknowledging the impact of their products on public health, and I see no reason why the Government should not demand that manufacturers of processed food and fast-food chains do the same; at a time when obesity costs the economy more than £2bn a year, and the NHS another £500m, it can hardly be argued that it is not the state's business what we eat. At the very least, it seems reasonable to expect McDonald's to warn its customers that a person eating a Big Mac and fries is consuming almost twice as many calories as someone sitting down to the same weight of pasta and salad.

Given the association between fast food, class and poverty, the people who habitually consume it are least likely to be aware of all the studies that warn about the effects of obesity; it is the middle classes who know that 31,000 people die prematurely each year because they are fat, and that being overweight is linked to a whole range of unpleasant conditions, from diabetes and cancer to heart disease. With the case against the fast-food companies growing stronger by the month, the Government has a duty to get this information across to the people who need it most, and the obvious place to put it is on the lids of burger cartons. Customers might feel differently about a Big Mac if they were told the stark fact that obesity reduces their life expectancy by an average of nine years.