The researchers found that there has been no reduction in the energy we expend on day to day activities over the last 20 years, suggesting increased food intake may be the more important factor in obesity.

Previously the increase in the prevalence of obesity throughout the Western world over the past 20 to 30 years has commonly been blamed on lifestyle trends such as increased car ownership, children been driven rather than walking to school, and the increase in television channels and computer gaming. 

Currently over 20 per cent of the population in the USA and the UK have a BMI over 30 and so are classed as obese. Scotland has the second highest rate of obesity in the world, next to America.  

Professor John Speakman, University of Aberdeen, who co-authored a paper from the research that has been published online in the International Journal of Obesity, 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.”   

While fellow co-author, Professor Klaas Westerterp, from the University of Maastricht, added:   

“Because we found no evidence for declines in energy expenditure over the last two decades, this work suggests that the obesity epidemic has been largely driven by increases in food intake.” 

Professor Michael Goran, Professor of Preventive Medicine and Director of the Childhood Obesity Research Center at the University of Southern California who is an international expert in the study of obesity, added: “This is an important study that puts into question a commonly held belief that the surge in obesity over the last few decades can be simply explained by a more sedentary lifestyle.”