A new study says it has debunked a widely accepted theory in the medical community that a sedentary lifestyle leads to obesity. Instead, the research has connected excess weight with overeating.

The basis of this new medical claim is a study by Prof. John Speakman of the University of Aberdeen, who compared energy levels of Americans and Europeans in the past two decades.

"We found that people have not reduced their energy expenditure over the same period that obesity rates have increased enormously," Speakman said, quoted by the U.K. Telegraph. He added, "It seems that we have been misled by the anecdotal information about levels of our physical activity. When actual measurements of energy expenditure are analyzed there is no evidence for a reduction over time."

The study, published in the International Journal of Obesity, measured the survey participants' energy demand as they went through their daily lives using the isotope-based technique.

The findings suggested an increase in food intake as the main cause of obesity, rather than lack of exercise or physical activity or a couch-potato lifestyle, said Prof. Klass Westerterp of the University of Maastricht, a co-author of the study.

Meanwhile, the food industry said that it has done its share in educating the public about proper nutrition through product labeling. Justin King, chief executive of J Sainsbury, U.K.'s third largest supermarket, said it is about time government does it share in cutting obesity rates in Britain by pushing for a massive educational campaign focused on healthier lifestyles.