Over-Eating Blamed for US obesity

Over-eating, not a lack of exercise, is to blame for the American obesity epidemic, a new study claimed, warning that physical activity could not fully compensate for excess kilojoules.

“There is no evidence that a marked reduction in physical activity has been a contributor to this epidemic in the US,” study leader Boyd Swinburn said. “The increase in energy intake… virtually explained all of the weight gain.”

Swinburn, a professor at the health faculty of Australia’s Deakin University, said American children had grown on average 4kgs heavier over the past three decades with adults putting on an extra 8kgs.

The study calculated what Americans should weigh today based on their current, higher food intake, and comparing this to their actual weight. If they weighed more than projected, this would suggest a drop in physical activity.

Adults increasing activity
In fact, researchers found that American adults weighed less than could be expected from their diet, “which means that if anything over that period of time, the adults had been increasing their physical activity, not decreasing,” said Swinburn.

Among children, the tests yielded a 100% match, leading researchers to conclude that changes in physical activity had had no impact whatsoever on America’s children growing fatter. The findings would “probably be similar” for other developed countries, Swinburn said.

For the US population to return to its leaner, 1970s self, children would have to cut their intake by about 1 470 kilojoules a day – equal to one can of fizzy drink and a small portion of French fries, and adults by about 2 100 kilojoules – the equivalent of a Big Mac burger.

Alternatively, children would have to walk for an extra two-and-a-half hours a day, and adults for nearly two hours, said Swinburn.

People need to eat less to lose weight
“Getting everybody to walk an extra two hours a day is not really a feasible option for countering the epidemic,” he said. “We need to limit our expectations of what an increase in physical activity can achieve.”

Swinburn stressed that the findings did not seek to negate the value of physical activity for weight control and overall health. “But if we want to influence the underlying drivers (behind obesity), we have to have our eye much more on the energy intake side than on the physical activity side.”

In short, Americans must eat less, he said. The World Health Organisation estimates that in 2005, about 1.6 billion adults were overweight, of which at least 400 million were obese. The conference was organised by the European Association for the Study of Obesity. – (Sapa, May 2009)