A computer firm boss has amazed his office colleagues by getting a beach body which would be the envy of men half his age in just six months.

Colin Sinclair set out on his rigorous exercise programme to raise money for the Special Care Baby Unit that nursed his son back to fitness 20 years ago.

Premature Erin tipped the scales at just 1lb 11oz when he was born at 26 weeks – the lightest baby ever cared for by the Special Care Baby Unit at York Hospital.

The infant spent four months in an incubator and was placed on oxygen and antibiotics to battle a range of infections.

His heart stopped several times before he gained enough weight for his parents to take him home after six months – by which time he weighed only 4lbs.

But Erin is now a strapping 20-year-old. Although his dad had always kept himself fit, the 50-year-old could not help noticing a slight paunch six months ago.

But after going to the gym four or five nights a week Colin was confident enough in his new chiselled look to enter a body-building contest by The National Physique Association.

After following a sugar and takeaway-free diet, he has seen his weight plummet from 82 kilos to 69 kilos – and his waistline shrink from 32ins to 27ins.

Colin, of Stillingfleet, has also seen his shoulders, arms, and chest bulk up. His untoned belly has become a six pack.

Colin, a business development manager at Heslington-based software development firm Ap16, said friends and colleagues did not spot what was going on under his clothes.

He added: “It was only when I posted some photos that they realised. They have been absolutely amazed.”

He had set himself a time-table of six months to achieve a holiday-ready body – the time it took his son to get past the worst of his health problems.

Mr Sinclair Snr had always been reasonably lean and wanted to show the results that could be achieved with some simple lifestyle changes.

So far he has raised £700 for the unit. To contribute visit: http://www.justgiving.com/colin-sinclair1.