The number of diabetes sufferers is expected to double in Britain over the next ten years, causing a huge increase in deaths from heart disease.

Yet many could ward off the threat of diabetes in middle age or reduce its impact by abandoning their ‘couch potato’ lifestyles, the British Heart Foundation and Diabetes UK say today.

Diabetes drastically increases the risk of death from cardiovascular disease. But many sufferers are unaware of the added danger and do nothing to protect themselves.

There has been a rapid rise in cases of Type 2 - non-insulin dependent - diabetes.

Yet eating a healthy diet, losing weight and taking regular exercise could prevent diabetes and lower the risk of heart problems in diabetics, according to Professor Sir Charles George, the foundation’s medical director.

‘The predicted doubling of diabetes by 2010 and the resulting rise in cardiovascular disease are not inevitable,’ he said. ‘We know how to prevent them. Now is the time to act together to save lives.’

About 1.4 million Britons are diagnosed as having diabetes, nine in ten of them with Type 2. But the true figure could be double that.

Although heart disease and strokes remain the UK’s biggest killer, claiming more than 150,000 lives a year, there has been a steady decline over the past 20 years.

The two charities say the decrease is unlikely to continue unless the ‘diabetes timebomb’ is defused.

Women aged 40-59 with diabetes are up to eight times more likely to develop cardiovascular disease while the risk for men is fivefold.