Obese people are more likely to be stuck in a "vicious cycle" of poverty because they perform poorly in school and miss out on jobs, researchers say.

A report, by the New Zealand Institute of Economic Research, said adults living in poor areas were 1.6 times as likely to be obese as those in other areas, and "face challenges at lifting their socio-economic status", starting with lower education.

"Obese children don't tend to do as well academically as their peers," the report said.

"Those lead in turn to lower wages, employment and social deprivation which increase the likelihood of obesity."

Challenges included workplace discrimination, increased sick leave and higher fuel and infrastructure costs including the need for larger seats and hospital beds, it said.

Edgar National Centre for Diabetes and Obesity Research director Professor Jim Mann said low socio-economic status was a "vicious cycle" for those with obesity.

"Being economically disadvantaged is a predisposing factor to obesity. One reason is good food preparation requires either time or money. If you are rich you can get good food or if you have a lot of time you can soak the lentils, et cetera.

"Once you are obese it also feeds socio-economic disadvantage because . . . you are too exhausted to work, getting jobs if more difficult, people are prejudiced against obese people and people are less likely to employ you - this is the vicious cycle."

Obese people often felt prejudged at job interviews, he said.

"Often they are embarrassed about their weight. It is again self-perpetuating. They feel that you may feel prejudicial against them so they present themselves less well. It is a horrible cycle."

Countering the high economic and social costs started with the surrounding environment, said Mann.

"If people are not bombarded with high saturated fat, high sugar kind of food everywhere they go . . . if you didn't have people who are socio-economically disadvantaged you would lose an enormous amount of obesity.

"The most important thing is to create an environment that reduces the risk of obesity, then when people are obese, is to be very sympathetic towards them and not prejudicial."

Loss of productivity due to excess weight was estimated to cost between $98 million and $225m in 2006.