LONDON (AP) _ Obese people who exercise have half the death rate of those who are trim but don't exercise, a leading expert said Tuesday.
Previous studies linking obesity and death from heart disease and other major killers have missed the important influence of exercise, said Steven Blair, director of research at the Cooper Institute for Aerobics Research in Dallas.
``There is a misdirected obsession with weight and weight loss,'' he told a meeting of the Association for the Study of Obesity in London. ``The focus is all wrong. It's fitness that is the key.''
However, some experts cautioned that reaching an appropriate weight is still advisable for preventing other complications of obesity that are not thought to be related to fitness, such as cancer, arthritis and infertility. The ideal is still trim and fit, they said.
``When you look at the data and the number of subjects he's studied and you recognize that Steve is an excellent scientist, I think nobody would say the data are flawed,'' said Dr. Susan Jebb, director of the Human Nutrition Unit at Cambridge University in England.
``I think that's good news for people who are overweight because it kind of gives them two options. You don't have to lose weight. You can instead improve your fitness,'' she said. ``However, the reality is that both of those are quite tough challenges. The question is just how many people do manage the level of fitness that he is showing is beneficial?''
Blair said that about 50 percent of the obese people in his studies were fit. It is unclear how that compares with the rate of fitness among obese people in the general population.
The studies involved 25,000 middle-aged men and about 8,000 women who were followed for 10 years. Fitness was measured by a standard stress test _ how long people could walk on a treadmill at increasing intensity before becoming exhausted.
The bottom 20 percent of the group were considered unfit.
The findings were the same whether obesity was measured by a body mass index (derived by multiplying a person's weight in pounds by 703 and dividing that result by height in inches squared), or by the percentage of body fat relative to muscle and bone, which meant the results were not due to heavy people simply being well muscled, Blair said.
People with a body mass index of 30 or more are considered obese.
The United States leads the world in population of overweight men and women. The U.S. Centers for Disease Control and Prevention estimates that 61 percent of Americans are overweight and 26 percent are obese, or grossly overweight.
Blair said 30 minutes of moderate walking every day, at three or four mph, would make most obese people fit.
``To put yourself in our top fitness category, you might walk more vigorously and add a couple of games of tennis at the weekends,'' he said.
Some other fitness experts recommend 60 minutes a day of exercise for health.
``I don't mean it eliminates the risk of everything, but you can stay overweight and obese if you are fit and be just as healthy, in terms of mortality risk, as a lean fit person,'' Blair said. ``When they talk about the health risks of obesity, they usually talk about heart disease, diabetes _ the big killers.''
``We have also looked at disease rates, particularly diabetes. The phenomenon holds there too that the obese individuals who are fit develop diabetes at about the same rate as the lean individuals who are unfit,'' he said.
People might still want to shed pounds for other reasons _ so that they can fit more comfortably into an airline seat or to stop others discrimination, Blair said.
``I'm inclined to agree with that. I don't think that carrying around a lot of fat, in itself, is necessarily detrimental because a number of large people are very vigorous,'' said John E. Blundell, chair of psychobiology at the University of Leeds in England.
``Thin and active is probably the optimal because that way you are no longer a target of the culture, you don't receive that psychological damage of being stigmatized,'' he said.