Many obese teenagers face heart attacks in their 40s, the medical director of the British Heart Foundation warned yesterday.

Peter Weissberg suggested that a long, downward trend in people dying from heart disease was "the lull before the storm".

In one of the starkest predictions yet of the consequences for young people fed on junk food and doing little exercise, he said: "The current cohort of obese teenagers is heading for heart attacks in their 40s if they get type-2 diabetes, and many of them will."

Prof Weissberg's remarks contrast with the government's optimistic projections that within the next 10 years virtually no one under 65 will be dying from heart disease. Although new treatments and drugs may extend the survival rate of those who have had a heart attack beyond the current 50%, the suggestion that a large proportion of people in their 40s will suffer such serious medical events within the next 30 years points to the death rate in middle age getting worse again.

The government has outlined in its public health white paper a programme to tackle the issue and to reduce the number of obese young people. One in six under-16s now falls into that category.

The foundation also wants to dispel any suggestion that surviving a heart attack or other forms of serious coronary damage means a return to normal life.

Prof Weissberg, a cardiologist in Cambridge, said many people were unaware of the impact of living with heart disease. Hospitals were often "pretty powerless" to do anything for patients who were sent home "to slowly die".

The warnings were made as the foundation began an appeal to fund more specialist heart nurses in patients' homes. It currently funds 180, helping about 50,000 of Britain's 2.7 million heart patients. The aim is to fund another 30, reaching a further 10,000 patients. It is unclear how many are funded by the NHS, although support generally is patchy across the country.

A survey of more than 1,000 people conducted for the foundation showed that more people were concerned about developing cancer (49%) or Alzheimer's (19%) than heart disease (11%). Forty per cent believed that heart disease would affect their lives "slightly" and just 2% that it would have a major effect.

But 59% recognised that heart disease was not "a quick way to go", compared with 52% thinking in 2002 that it meant a rapid death.

Prof Weissberg said: "This survey suggests people do not fear heart disease as much as cancer or Alzheimer's because they think that, while they may have to live with heart disease for many years, it would be a relatively easy disease to live with. Sadly this is rarely the case.

"Thousands of people each year have to deal with the fact their hearts are permanently damaged."

Any hope of using stem cell treatments to repair hearts was probably 10 to 15 years away.

Heart disease still kills 17,500 Britons a year but the figure has been falling since the 1970s. However that has meant many more living with the disease, a problem that will get greater as the population ages, even if the prediction for today's teenagers does not come to pass.

Roger Boyle, the NHS's national clinical director of heart disease, admitted in a contribution to the foundation's report on the issue, that there was a still a "mixed picture" even though the government was investing heavily in tackling the problem.

About one in three people who should be on registers of patients with heart disease were not known to their GPs and were not receiving the care they needed.