Estimated health impacts of reformulation resulting from Health Star Rating nutrition labelling in Aotearoa New Zealand

We aimed to model the impact of product reformulation following adoption of the Health Star Rating (HSR) nutrition labelling system in Aotearoa New Zealand (NZ). Household panel data (2014-19) was used to estimate the effect of HSR labels on product nutrient content. Observed changes were applied to population dietary intakes. Impacts were modelled through to Health Adjusted Life Years (HALYs) and health sector costs (NZ$2011 consumer price index (CPI) adjusted to NZ$2023) using a proportional multi-state life-table (pMSLT) model over the remaining life of the 2011 NZ population (<i>n </i>= 4.4 million, 3% discounted). Modelling the current HSR uptake (23% products on average), NZ adults' mean daily energy, sodium and fibre intakes changed by 0.7 KJ (0.0%), -18.2 mg (-0.5%) and 0.04 g (0.2%). This resulted in 700 (95% uncertainty interval (UI): -600-1,800) HALYs gained, and estimated net costs (combining intervention costs and health system cost savings) of $8.4 million (M, 95% UI: -$17.4 to $35.4M). An estimated 24,300 HALYs (95% UI: 19,400-29,900) and $568.1M (95% UI: $430.1 to $733.7M) cost savings were seen if the HSR was made mandatory in 2025. The results of the current HSR uptake find minimal reformulation causing very small changes in population nutrient intake and therefore resulting in small health gains. Mandatory HSR nutrition labels could deliver population health gains and health sector cost savings through reformulation. There is, however, real uncertainty around the scheme's effect on energy intake which will affect these impacts.