Adults living in the most-deprived areas are 1.5 times as likely to be obese as those in the least-deprived areas.
FitCo Tauranga staff member Donna Logan said the gym saw "all shapes, all sizes" but a noticeable trend was more bigger kids aged about 12 or 13 coming in.
"Sometimes it's sad too, because they are young but they are overweight.
"These days they don't [run around], they just sit at their computers or their games and things and eat their junk."
Clients rushed to join up for summer in October but December was a quiet month.
More clients joined up in January after making New Year's resolutions to get fit, she said.
Between 50-60 per cent of those clients kept up their gym routine.
The Ministry of Health survey shows 11 per cent of children aged 2-14 years are obese, which amounts to about 85,000 youngsters. The childhood obesity rate is similar to last year's but has increased significantly since 2006-07.
Heart Foundation medical director Norman Sharpe said the newly released figures for adults were "fearful" but not surprising. The rising rate of childhood obesity was disappointing.
"That, to me, is the greatest concern."
Although slight statistical differences within different surveys were likely, obesity in children had "gone onward and upward," Professor Sharpe said.
"That's where we need more of a long-term and visionary approach."
The Heart Foundation is calling for political parties to draw up a comprehensive food and nutrition plan for children, including making healthy food more affordable and accessible for families, a front of pack labelling system on food, a tax and/or other regulatory measures on sugary soft drinks, regulation of advertising of unhealthy foods to children, and ensuring schools and preschools provide healthy food environments.
Health Minister Tony Ryall has rejected any "nanny state" measures, instead arguing that providing information and support to people is enough.
"In the end, the Government can pass all the laws it likes but, unless people eat less and exercise more, things won't change," Mr Ryall said.
The Government focus for new nutrition programmes has been on mothers and babies. It is also spending more on screening for diabetes and cardiovascular disease, and on providing more "green prescriptions" in which GPs and nurses encourage patients to get exercise and improve their diet.
The ministry expects to release regional obesity figures in early 2014.APNZ
