Number of cancer patients will increase due to obesity - dietician

New Zealand's health system could be in for a shock as higher obesity rates could lead to higher cancer rates.

Oncology dietician Julie Beadel told The AM Show there are 12 cancers linked to body fat, and our obesity rates aren't good news for the health system.

"The population of obese children is going to turn into obese adults so the risk of cancer is going to increase and the number of cancer patients is going to increase."

New research out of the UK shows obesity is about to overtake smoking as the leading cause of cancer. 

Beadel said excess body fat increases inflammation in the body, as well as the amount of hormones, which can push up a person's risk of cancer.

Unfortunately a lot of people are set up to fail when fighting obesity.

"The wrong sorts of foods are available too easily now, you can't go and buy petrol without being faced with two cans of energy on special," Beadel said.

She said one thing people can do to lower their body fat and therefore their risk of cancer is get out moving.

"The second biggest recommendation that the world cancer fund make is you should do 30-60 minutes of excersise a day and one of those things, I think, is walking.

"I say to my patients that walking is just as good as anything, you don't have to be running up a hill, doing iron man things, walking is good."

She also suggested changes to diet, ensuring people eat more fruits and vegetables, whole grains and legumes.