Lazy lifestyle blamed for rise in obesity

Lack of physical exercise is the cause of Britain's rapid, dangerous and extremely expensive increase in obesity over the past two decades, scientists agreed yesterday. Illnesses such as heart disease related to excessive fat are reckoned to cost the NHS pounds 2bn a year - 6 per cent of its total budget.

On average, people actually eat less than they did 20 years ago and they even eat less total fat. But populations in Western countries like Britain are still fattening up, putting on a gram a day on average or nearly a pound a year.

Obesity was a major theme at the British Association of Advancement of Science's week-long festival in Leeds yesterday, as researchers summarised the state of play.

Science broadcaster and former BBC Tomorrow's World presenter Judith Hann also delivered a stern lecture against lazy eating habits, lazy parents, convenience foods and the decline in families eating together.

Dr Andrew Prentice, of the Medical Research Council's clinical nutrition centre in Cambridge, said more and more genes were being discovered which pre-disposed people to obesity. But genetics could not be blamed for the spread of obesity - the genes had not changed while the population had become distinctly fatter.

Very obese women were 100 times more likely to develop diabetes, and even slightly overweight people "which covers many of us in this audience" were at 10 times higher risk, said Dr Prentice.

Strictly controlled experiments had shown that while fat people often blamed their weight on a low metabolism, they almost always have a normal or higher metabolism than average, Dr Prentice said. This was because they develop more muscle tissue to shift their extra bulk around. Fat people had been notoriously difficult to study, he said, because they invariably underestimated the amount they eat when asked by researchers to log their diet, or started eating less than they normally would when under scrutiny.

The proportion of fat in the average diet has increased as people have eaten more luxurious foods and meat. The body is much quicker to metabolise protein, carbohydrates and alcohol than fat. But since, overall, people are eating less food and less total fat than they did 20 years ago, the marked increase in obesity during that period is pinned firmly on the decline of exercise.

Dr Prentice pointed to the spread of labour-saving devices, from the television remote control to the lift and the escalator. Car ownership has also grown rapidly: while the great majority of children walked to school in the 1960s the opposite is now true. Put together, all contribute to a reduction in the amount of exercise that most people take. However, Dr Prentice said he took hope from the strong link between obesity and levels of earnings and education. If the population became more affluent and better educated the tide of rising obesity could be turned.

The absence of a piece of DNA containing just 17 genes can cause a huge range of birth abnormalities, including heart defects, immune-system deficiencies and cleft palate, writes Charles Arthur.

Adults who lack the same stretch of genetic material are also more likely to develop obsessive-compulsive disorders, such as excessive hand-washing, John Burn, professor of clinical genetics at Newcastle University, told the meeting.

The block of DNA responsible for the problems normally lies on the main part of chromosome 22, of the 23 pairs of human chromosomes. It is about 2 million base pairs long, and contains 17 gene locations. In people with problems, the genes "are known to be missing, but we don't know which is the important one", said Professor Burn. Studies are now under way to try to pin it down.