Obesity researchers from the Universities of Aberdeen and Maastricht in the Netherlands have discovered we burn the same calories on physical activities as we have done over the last 20 years.
Currently over 20% of the population in the USA and the UK are classed as obese with an additional 30 to 40% classed as overweight. The problem has been blamed on people eating too much, or exercising too little, or a combination of both.
Consensus over the past few years has been that an increased sedentary lifestyle has been a major contributory factor. This view is consistent with perceived lifestyle trends such as increased car ownership; children being driven, rather than walking, to school, and the boom in television channels and computer gaming.
The researchers found that there has been no reduction in the energy we expend on day-to-day activities, suggesting increased food intake may be the more important factor in obesity.
They also found that comparisons of energy expended by people in both the USA and Europe differ little from those in preindustrial societies in the Third World. Even more surprising, these levels were also the same as those anticipated from studies of wild animals.
Professor John Speakman, from the University of Aberdeen, said: "We found that people have not reduced their energy expenditure over the same period that obesity rates have increased enormously.
"It seems that we have been misled by the anecdotal information about levels of our physical activity. When actual measurements of energy expenditure are analysed there is no evidence for a reduction over time."