How to change food choices for the climate

What type of interventions work?

People in high-income countries tend to eat far more animal-based foods than recommended for their health. A shift to a more plant-based diet has the potential to not only reduce the risk of health problems such as heart disease and diabetes, but also to reduce greenhouse gas emissions. This is one example of the so-called ‘co-benefits’ of climate action for health.

Food choices are complex. The best way to influence those choices is not clear. A new systematic review, published in The Lancet Planetary Health, explores how effective different interventions have been in shifting people to sustainable diets.

The review

Researchers from Central London Community Healthcare NHS Trust, Sheffield Hallam University and the London School of Hygiene & Tropical Medicine conducted the review.

They identified 13 studies which met their criteria, from six countries (Canada, Germany, Italy, the Netherlands, the UK and the USA). The studies focused on individual-level interventions aimed at adults and children.

The team looked at data on outcomes including: reduction in food waste; changes in meat consumption; changes in plant-based consumption; changes in dietary greenhouse gas emissions; and health outcomes.

The review classified interventions using a behaviour change wheel, which categorises interventions into nine ‘functions’, such as persuasion, education, or incentivisation. The review set out to establish what types of interventions are effective in changing individual dietary behaviour.

What works?

The studies were varied, which makes them hard to compare. Some were delivered online, others in universities or schools, via text messages, in a laboratory, or to participants at home. Follow-up with participants lasted from one week to five months.

Nine studies reported a change in diet, with those successfully focused on meat consumption reporting a mean reduction of 1.47 portions of red or processed meat per week. Three studies reported reduced food waste.

Five studies reported on greenhouse gas emissions, for example, one reported a reduction of 10.5kg of carbon dioxide equivalent per week and another 1.48kg.

Assessing the interventions against the behaviour change wheel, 11 of the 13 studies were found to have used ‘education’, 5 used ‘persuasion’, 4 used ‘training’, 3 used ‘modelling’, 2 used ‘environmental restructuring’, and 1 used ‘restriction’.

‘Education’ included presentations, posters and text messages. Two studies compared whether educational messages were framed as having an environmental or a health benefit and reported that an environmental framing resulted in greater reductions in meat consumption.

Four studies used ‘training’, including through instructions on how to reduce meat consumption and recipes for plant-based meals.

Five studies used ‘persuasion’ and all five resulted in significant reductions in meat consumption or food waste. Methods categorised as using persuasion included: text messages using ‘anticipated regret’; a request to reduce processed meat consumption or food waste; and online nudges.

Two studies used ‘environmental restructuring’ by providing free meat substitutes and reducing portion sizes of meat dishes in a canteen to reduce food waste.

The review found that interventions using education had the most robust evidence, and interventions which used persuasion had the strongest effect on reducing meat consumption.

Interventions using education in combination with other factors had the most success. The authors conclude that, “on the basis of the findings from this systematic review, multicomponent interventions are more effective at shifting dietary behaviour than single component interventions.”

The authors acknowledge that it is difficult to draw conclusions from the review, given the small number of very varied studies, but nonetheless it provides an interesting overview and insight into existing published work in this area.

Reference

Wadi N et al. Investigating intervention components and their effectiveness in promoting environmentally sustainable diets: a systematic review. The Lancet Planetary Health, 8(6), E410-E422, 2024. https://doi.org/10.1016/S2542-5196(24)00064-0