Cancers potentially attributable to excess body weight in Aotearoa New Zealand from 2019 to 2023

This study quantifies the incidence of cancers attributable to excess body weight (EBW) in Aotearoa New Zealand adults aged 30+ from 2019 to 2023 and assesses public health implications.

Relative risk estimates from an existing review and EBW prevalence from the New Zealand Health Survey were used to calculate population attributable fractions (PAFs) for 12 cancer types. PAFs were applied to Cancer Registry data to estimate EBW-attributable cases. Confidence intervals were calculated using bootstrap techniques. Two scenarios explored the potential impact of reducing EBW prevalence.

An estimated 6,962 cancers (5.1% of all cases) were potentially attributable to EBW, averaging 1,390 cases annually. The impact was greater for females (PAF 6.3%) than males (PAF 4.1%). Among Māori, 6.9% of cancers (221 per year) were attributed to EBW, while Pacific peoples had a higher PAF of 11.8% (145 cases per year). PAFs were highest for Pacific females (16.1%, 110 per year). Modelling suggests halving EBW prevalence could potentially prevent 600 cases annually.

EBW contributes to a large number of cancers in New Zealand, compounding health inequities, particularly for Māori and Pacific peoples. These inequities highlight the urgent need for multisectoral, collaborative interventions that address the complex, inequitable drivers of EBW. Public health must strengthen its pro-equity, anti-stigmatising approach to prevention, management and treatment. However, sustained reductions in EBW-related cancers will ultimately depend on preventing EBW rather than relying on treatment-based interventions.