A medical specialist dealing with obese people has challenged decisions by NHS trusts to deny hip and knee replacement surgery to overweight patients.
Last month it emerged that obese people would not be entitled to such surgery on the NHS in East Suffolk.
The ruling was made by three primary care trusts in an attempt to save cash.
Nicholas Finer, a consultant in obesity medicine at Addenbrooke's Hospital in Cambridge, said there was no evidence that their replacement joints wore out.
Some experts say that the risks of operating on obese patients are higher and the treatment may be less effective, with replacement joints wearing out sooner.
But Dr Finer, writing in the British Medical Journal, said: "No evidence supports withholding joint replacement from obese people, even on utilitarian grounds.
"Since obesity does not increase the risks or diminish the benefits of joint replacement, the trust's decision to deny such treatment seems to be based on prejudice or attribution of fault, or both."
Dr Brian Keeble, director of public health for Ipswich PCT, has said operating in such cases could be detrimental to patients because of the risk of side effects.
He also blamed the "pressing financial problems" of the NHS in East Suffolk for the move.