Human obesity has reached pandemic proportions. More than 1.9 billion adults worldwide are now overweight. Of these, 600 million are classed as obese. Around 3 million people die each year as a result of being overweight or obese. This is a problem for the entire global community, not only high-income countries, and action can be taken.
Environmental costs of food production are very high, with agriculture a key driver of water scarcity. Irrigation accounts for approximately 70 per cent of freshwater withdrawals around the world – up to 90 per cent in some low- and middle-income countries (LMICs). Food production is also responsible for 30 per cent of greenhouse gas emissions. These impacts are unsustainable.
What is good for public health is often good for the environment. However, rising to the challenge of changing patterns of food consumption on the scale needed to have an impact at the global level is a complex task. Behaviour can be influenced through many different approaches.
There is no single definition of a healthy and sustainable diet. The range of relevant eating behaviours is large, and although the reduction of some dietary constituents – such as red and processed meat – can offer clear co-benefits for health and sustainability, in other areas, ‘win-wins’ may not be possible.
Most research on interventions is concerned with either health or sustainability objectives, but evidence on interventions designed to achieve co-benefits is scarce. There is also a lack of evidence on interventions in LMICs. This is an obstacle to progress, since high population and economic growth, along with rapid urbanization, mean that it is in LMICs that much of the increase in consumption of unhealthy and unsustainable foods will occur in the future.
The available evidence is strongest for the impact of fiscal and restrictive measures. In isolation, neither information provision nor ‘nudges’ appear likely to change consumption patterns sufficiently at the population level. However, combination strategies are likely to be important.
The evidence highlights the risk of unintended consequences, such as leakage and substitution effects, rebound effects and ‘halo’ effects. Modelling can help anticipate some of these factors, and independent evaluation can be incorporated into interventions, not only to build evidence but also to monitor unintended consequences and inform modifications to policy and strategy.
This paper offers a preliminary overview of the available evidence for interventions, to inform policy decisions for strategies aimed at encouraging healthy and sustainable diets. It is intended to promote discussion and follow-on activities.
Literature review: Policies and actions to shift eating patterns: What works?