AN INTERNATIONALLY esteemed expert on obesity has hit out at the "hysteria" surrounding the subject ahead of a major conference in Edinburgh tomorrow.

Australian academic Dr Michael Gard - lead author of The Obesity Epidemic: Science, Morality and Ideology - will speak at the Holyrood Magazine conference on childhood obesity at the Balmoral Hotel. The event is bringing together leading thinkers and practitioners from across the globe to debate how best to tackle the spiralling problem, and to highlight lessons Scotland can draw from other nations' experiences. It follows the launch earlier this year of the Scottish government's £40 million anti-obesity initiative, Healthy Eating, Active Living.

The rate of childhood obesity has trebled in the past 20 years and, if current trends continue, half of British children will be obese by 2020. Health watchdog, ScotPHO, reported in January that a fifth of Scottish boys and one in 10 girls aged two to 15 fall into that category - leaving many commentators to believe we are facing a public health timebomb.

But Gard told the Sunday Herald that there are indications that obesity has plateaued. "Across the world now there are quite clear signs, particularly among white groups and middle-class groups, that the problem is beginning to level out - as was inevitable. A large study in New South Wales found the average rise there was mainly attributable to ethnic minority groups. We don't know why, but white middle-class people have always been very responsive to public health messages. Also, it was never really going up that quickly - it was increasing from a low base. It was inevitable that it would level out."

Gard believes the issue has been overstated. "I have said all along that obesity is one of the leading health problems we face, but those people who said it was a crisis or an epidemic didn't help matters because we weren't able to put the thing in proper perspective.

"Now what is happening is that, as the hysteria dies down, we will just get down to treating obesity as the run-of-the-mill public health issue that it is. Once we get past calling it a crisis' we will probably start to get somewhere. It was never going to cripple anyone's health system, as was predicted. It was never going to bring health systems to their knees. It was never going to lead to reductions in life expectancy - and the evidence is accumulating on that."

For the past 25 years, government health surveys in Australia have shown the population on average living longer, getting healthier and enjoying a better quality of life. Concurrently, levels of obesity rocketed to a point where Australians became the third-fattest Western nation. They are still in the top six.

Dr Jason Gill, a senior lecturer in integrative and systems biology at Glasgow University believes it is too early into the "epidemic" to judge the impact of obesity on life expectancy - and that it should probably be measured in years of health, rather than years of life.

"What's happened is we've become better at managing cardiovascular disease. We're good at giving people cholesterol-lowering drugs, drugs that reduce blood pressure and the surgical interventions which help people survive better from heart attacks and live longer.

"If we become better at treating these conditions, it won't necessarily reflect in life expectancy but the healthspan' - how long you live in good health - might actually reduce, and that's probably a more helpful gauge. The obesity epidemic has really only come on in the last 20 years, so it's probably too early to judge its effect on average life expectancy. People dying now in their 70s and 80s haven't been exposed to the trend. The next 20 years will probably give us a better idea."

While the problem may appear out of control, research suggests small changes can deliver pay-offs. "The issue is whether they even need to become normal' weight - a lot of evidence suggests they don't," says Gill. "If you lose 5-10% of your bodyweight you can normalise your metabolism in terms of blood pressure, glucose and lipid levels in the blood. So that's a positive message."