Calls for a ‘fat tax’ on food have been criticised by a clinically obese man who is awaiting NHS weight loss surgery.

Medical experts from Oxford University have recommended a 20 per cent tax is imposed on unhealthy food and fizzy drinks to tackle the numbers of people suffering diet-related conditions such as obesity and heart disease.

They have also recommended there should be subsidies on healthy foods such as fruit and vegetables.

Dr Oliver Mytton and Dr Mike Rayner of the Department of Public Health at Oxford authored the report which was published in the BMJ health journal yesterday.

Dr Mytton said studies carried out at the university suggested extending VAT on unhealthy foods in the UK could cut up to 2,700 heart disease deaths a year.

But Michael Treadwell, from Trefoil Place in Greater Leys, said the attitude was unrealistic. Mr Treadwell used to weigh 27 stone and at 5ft 10ins had a Body Mass Index (BMI) of 54 making him super-obese. Someone of a healthy weight have a BMI of about 25.

He has managed to slim down to 20 stone giving him a BMIof about 40 and will have a gastric bypass next month, paid for by the NHS. Mr Treadwell, 47, said most severely overweight people had tried ‘every diet under the sun’ to lose weight and many were born into big families.

But he said healthy food simply ‘cost too much’.

He said: “I agree there should be subsidies for fruit and vegetables and I see why they do carry out these studies. But it is all very well for them to sit in their ivory towers and say ‘oh eat healthily and you will lose weight’.

“But for people on benefits, such as myself, it’s difficult enough to buy food as it is. It is much cheaper to eat unhealthy food. I know these studies are done for a reason, but I’m not sure this is the answer.”

Mr Treadwell suffers from type two diabetes, hypertension and sleep apnoea – a condition whereby sufferers stop breathing during sleep – and takes a cocktail of six pills a day for a host of other ailments.

He said he has always eaten a relatively healthy diet, with plenty of fruit and vegetables.

But his weight rocketed when he would drink up to 12 pints of lager a night. He has since lost weight by quitting drinking.

Dr Rayner said government intervention such as taxation can be justified when the market fails to provide the ‘optimum’ good for society’s well-being.

He said: “Obesity has rocketed recently and if anything our diet is getting worse. We need to take steps to tackle this problem as a nation. It’s affecting our health and it’s affecting our wallets through the increased burden on the NHS and the taxpayer.

“It is basic economic theory that raising the price will change consumption, and we already use the taxation system in this way to influence behaviour.”