Table 1 PICOS approach to study eligibility*

Healthy populations (any age or gender), from any country

Studies including participants that were not representative of the population were excluded (e.g. sub categories such as obese participants in weight loss trials, participants with diabetes, pregnant women).

Studies evaluating the effects of intervention to promote healthy eating that were implemented experimentally; or due to local or national policies. These could include a range of actions to improve healthy eating (in terms of the dietary factors of salt, sugar, trans fats, saturated fat, total fat, fruit and vegetables and calories).

Interventions with no change in healthy eating outcomes quantitatively stratified by SEP.

Actions initiated by industry.

Studies were only included in the review provided that the authors made a quantitative comparison of differential effects of policy interventions to improve healthy eating by at least one measure of SEP.

Studies which did not report the effects of actions to improve healthy eating by SEP

The primary outcome of interest was dietary intake. Secondary outcomes included: changes in clinical/physiological indicators related to NCD, behaviours associated with a healthy diet e.g. change in BMI.

Process evaluations reporting on implementation of interventions/policies without any outcome data; data only on costs, or feasibility or acceptability without an assessment of intake; reviews/studies of under-nutrition.

Studies with no mention of SEP.

We included studies of any design, including RCTs, cohort studies and modelling studies. We explicitly included modelling studies to better capture analysis of fiscal measures such as taxes, subsidies, or economic incentives

Opinion articles; purely qualitative evaluations with no quantitative assessment; data/statistics from monitoring and surveillance not directly linked to a policy intervention