To diet or not to diet, that is the question.

A leading nutritionist from Oxford University has waded into a debate on the affects of yo-yo dieting.

Professor of diet and population health at Oxford University Susan Jebb has pointed out it is better to try and lose weight than do nothing.

She said: "I agree with the notion that losing weight is generally worthwhile, even if you put the weight back on again.

"We have good evidence from long-term follow up studies after controlled intervention studies in humans that there is a benefit."

US biostatistician Dr David Allison found that repeated crash diets did no harm to obese mice.

In fact, serial dieting animals lived longer than those that remained obese.