Evidence on the effectiveness and equity of population-based policies to reduce the burden of type 2 diabetes: a narrative review.

There is increasing evidence for the effectiveness of population-based policies to reduce the burden of type 2 diabetes. Yet, there are concerns about the equity effects of some policies, whereby socioeconomically disadvantaged populations are not reached or are adversely affected. There is a lack of knowledge on the effectiveness and equity of policies that are both population based (i.e. targeting both at-risk and low-risk populations) and low agency (i.e. not requiring personal resources to benefit from the policy). In this narrative review, we selected 16 policies that were both population based and low agency and reviewed the evidence on their effectiveness and equity. Substantial evidence suggests that fruit and vegetable subsidies, unhealthy food taxes, mass media campaigns, and school nutrition and physical activity education are effective in promoting healthier lifestyle behaviours. Less evidence was available for mandatory food reformulation, reduced portion sizes, marketing restrictions and restriction of availability and promotion of unhealthy products, although the available evidence suggested that these policies were effective in reducing unhealthy food choices. Effects could rarely be quantified across different studies due to substantial heterogeneity. There is an overall lack of evidence on equity effects of population-based policies, although available studies mostly concluded that the policies had favourable equity effects, with the exception of food-labelling policies. Each of the policies is likely to have a relatively modest effect on population-level diabetes risks, which emphasises the importance of combining different policy measures. Future research should consider the type of evidence needed to demonstrate the real-world effectiveness and equity of population-based diabetes prevention policies.