Failed serial dieters who blame their weight problem on their genes, a slow metabolism or being "big boned", will no doubt gleefully adopt the concept, suggesting as it does that it is not their fault they are fat.
But passive over-eating, unlike passive smoking, offers no excuse for the victim, according to Dr Andrew Prentice of the Medical Research Council's Dunn Nutrition Centre in Cambridge. A low-fat diet and exercise remain the key to weight loss.
Speaking at the launch of a new healthy lifestyle initiative by the food and drink industry yesterday, Dr Prentice said there had been a 50 per cent increase in the fat to carbohydrate ratio in the national diet since the 1960s. "Food intake has been declining from its peak in the mid-1960s, so how is it that we have a burgeoning increase in obesity?" he asked.
"In part the reason is that although we are consuming a similar [or decreased] bulk of food there are many more calories per gram. It is passive over- eating - we don't necessarily want to eat more ... but neither we nor our bodies are recognising [the extra calories] and reducing the quantity of food accordingly."
But a predilection for fattier foods is only part of the story, and the increase in "sloth" may be a more significant factor, Dr Prentice said. A rapid decline in levels of physical activity has coincided with soaring obesity rates. Less than 6 per cent of children now walk to school, compared with up to 80 per cent in the 1950s and 1960s.
Television viewing has doubled from 13.5 hours in 1967 to 27 hours in 1992; people now spend 40 per cent of their leisure time watching TV, he added. "There are very few people who are doing anything like the energy expenditure needed to compensate for intake."
Dr Prentice said that weight-gain of Western populations had been the trend for 50-70 years. Boeing, the aircraft designer, had increased the weight allocation per passenger by 22lbs since it first started building aeroplanes. But it is the rise in the incidence of obesity - the number of obese British men and women doubled between 1980 and 1991 - which has alarmed doctors, who say that changing behaviour is the only way to tackle the problem, and reduce costs to the NHS of obesity-related problems, a figure now put at pounds 2bn.
The Government's Health of the Nation target to reduce the prevalence of obesity to 6 per cent of men and 8 per cent of women by 2005 is now regarded as over-ambitious, but the Food and Drink Federation said good progress towards the targets was possible. Its "Join the Activaters" initiative will focus on easy lifestyle changes.Reuse content