More than 1m prescriptions for obesity drugs were written last year, an eightfold rise in seven years. The rapid climb in the use of drugs, which doctors will normally prescribe only in severe cases, is clear evidence of the worsening problem. In 1999 GPs handed out 127,000 prescriptions. By 2006 they were writing 1.06m.

Most patients were given one of two drugs that were licensed in 1998 - orlistat (trade name Xenical), which prevents excess fat being absorbed by the body, or sibutramine (Reductil), which works in the brain to suppress the appetite. Both have side-effects and work only in conjunction with a diet.

Obesity drugs cost the NHS £47.5m last year, up from £4.9m in 1999. However, the government's Information Centre for Health and Social Care, which published the figures yesterday, said the cost of treating obesity and its consequences was between £990m and £1.2bn. That is between 2.3% and 2.6% of total NHS expenditure.

Figures in this report and from the Health Survey for England, which was published with it, contain conflicting evidence on the obesity epidemic. The number of children aged two to 15 who are obese rose from 11% in 1990 to 16% last year, but the proportion of obese girls dropped from 18% in 2005 to 15% in 2006. It is too soon to say whether this is a genuine downturn, says the information centre. Another positive sign is that exercise levels and consumption of fruit and vegetables are up. Last year 28% of women and 40% of men took at least 30 minutes of exercise five days a week, a rise from 21% and 32% in 1997. The proportions eating five or more portions of fruit and vegetables a day rose from 23% of men and 27% of women in 2004 to 28% and 32% in 2006. Children do less well but have also improved between 2004 and 2006, with 19% of boys (up from 13%) and 22% of girls (up from 12%) saying they eat five a day.

But the Health Survey for England shows more people are eating more fat than is recommended - up from 6% to 14% of men and from 3% to 7% of women since 2003 - and heart disease and diabetes associated with obesity have increased.

Rachel Craig, research director of the survey at the National Centre for Social Research, said: "While it is encouraging that there are signs people are beginning to improve their lifestyles ... many serious health conditions continue to increase and we need to do more to reduce risks of heart disease."

Betty McBride, head of policy at the British Heart Foundation, said: "Obesity drugs are clearly part of the solution for a minority of people. However, we are in danger of medicalising what is fundamentally a social problem.

"We face a stark choice - embrace a healthier lifestyle now or surrender to a nightmare future in which people rely on constant medication to treat an entirely preventable condition."