Inactivity is becoming a bigger epidemic than obesity, says expert in his 'Fat and Fit' conference address.

People get more health benefits from exercise than from dieting, says a sports physician.

And obese people who exercise regularly have a lower death rate than sedentary overweight or slender people, said Dr Chris Hanna.

"Recent evidence is telling us that inactivity is a bigger epidemic than obesity, and even in people who are overweight, moving is protective of their health."

He is speaking on 'Fat and Fit' at the annual scientific meeting of the Australian and New Zealand College of Anaesthetists in Auckland.

"Being active is more important than losing weight in terms of looking after health benefits," Dr Hanna told AAP.

He said a study had shown that obese people who are not fit have a rate of 62 deaths from all causes per '10,000 people years" compared to 18 for obese people who are moderately fit.

"And if you exercise and are obese your risk drops down below that of someone sedentary and of normal weight."

A healthy diet is equally as important as exercise, "but if you are looking at all-cause mortality you need to get off your bum and move and that's more important than losing weight."

As well as exercise such as walking, running and swimming, people should include strengthening and stretching, as well as balancing activities like yoga or tai chi.

"You should be looking after the whole body.

"And if you pick something you enjoy, you are more likely to do it."

* The writer travelled to Auckland courtesy of the ANZCA.