By Theresa Marteau, University of Cambridge, UK
Many of us struggle to eat more healthily, drink less alcohol, quit smoking, or walk instead of driving. This is true even when we know these changes would benefit our health and the planet. It applies to psychologists and behavioural scientists as well as the people we’re trying to help.
This struggle isn’t a failure of willpower. The problem is we consistently underestimate how much our everyday environments shape our behaviour, and overestimate the power of our values and intentions.
Why knowing isn’t enough
Consider personalised health predictions. Surely telling someone their exact risk of developing type 2 diabetes or heart disease would motivate change? The evidence says otherwise. Five systematic reviews including dozens of randomised controlled trials show that giving people personalised risk estimates—including genetic risk scores—has little or no impact on their behaviour. Rates of physical activity, smoking, alcohol consumption, and unhealthy eating remain unchanged.
Similarly, climate scientists possess detailed knowledge about climate change yet often fly as much as other academics. Knowledge alone rarely drives sustained behaviour change.
It’s the environment
Dual Process Models from behavioural science help explain this. Our behaviour is regulated by two interacting systems. One is slow, reflective, and goal-directed. We use it to read, learn new skills, and resist temptation. The other is fast, automatic, and cue-driven—when we see cake, we take it. When our limited reflective capacity is fully occupied, our automatic system responds directly to environmental cues. This is why changing the cues around us is more powerful than trying to change what’s in our heads.
The most powerful environmental cues fall under the 3 As: Affordability, Availability, and Appeal.
Affordability: Price changes behaviour
Increasing tobacco prices is the single most effective policy to reduce smoking. A 10% price increase reduces tobacco use by around 4 %. Soda taxes reduce consumption of sugary drinks. Fruit and vegetable consumption increases with subsidies to lower their price.
Availability: What’s accessible gets chosen
In a study with 20,000 employees across 19 workplace cafeterias, my research team increased the proportion of lower-calorie lunches offered and reduced portion sizes of higher-calorie meals. The result? Employees purchased 11.5% fewer calories as healthier options became easier to choose.
Appeal: Advertising works
Stopping advertising and sponsorships by the tobacco, alcohol, unhealthy food industries reduces the appeal and purchasing of their products. Similar effects are expected for fossil fuel products. Adding clear warning labels and removing branding from products also reduces their appeal. Labels on alcohol in Yukon, Canada, clearly warning of cancer from drinking, reduced alcohol sales by around 6 %. Plain packaging of tobacco renders warning labels more visible.
Why regulation matters
Most interventions that alter cues in our everyday environments to change behaviour require regulation because they conflict with commercial interests. Four industries—tobacco, alcohol, unhealthy food, and fossil fuels—generate products that cause at least one in four deaths globally each year, and the majority of greenhouse gas emissions warming the climate.
Yet information campaigns and voluntary industry self-regulation remain the favoured approaches. These industries actively promote this preference through lobbying, funding research that questions regulation, and framing government intervention as restricting freedom.
What needs to change
We need to shield evidence and policymaking from corporate interference. Tobacco control provides a model. Countries that have adopted Article 5.3 from the international treaty on tobacco control protected policymaking from industry interference, implemented more evidence-based policies, and have the lower rates of smoking. We need to extend this protection to cover all corporations generating products that ruin our health and wreck our planet. Citizen Assemblies and other forms of deliberative democracy in which citizens work collaboratively with our local or national governments also show much promise both in increasing citizens influence on policymaking and the influence of evidence.
Practical Recommendations
For healthcare practitioners
- Start with environments, not education. When working with clients or patients, identify the environmental cues triggering unwanted behaviours. Rather than focusing solely on motivation or knowledge, help people redesign their immediate surroundings. For example: keep fruit visible and processed snacks out of sight; place bikes in hallways rather than basements; use smaller plates and glasses.
- Advocate for workplace changes. Work with your institution to increase the availability and reduce the cost of healthier options in cafeterias. Simple changes like making plant-based meals the default with easy opt-outs can significantly shift behaviour.
For public health teams
- Make the invisible visible. Use your platforms to communicate how environments shape behaviour. Challenge the dominant narrative that behaviour change is primarily about individual willpower or knowledge. The evidence shows it’s about changing contexts, not just mindsets.
- Engage policymakers. Identify gaps between evidence and policies both locally and nationally. Write to policymakers with specific recommendations backed by evidence. Many are receptive to expert input, particularly when it includes practical solutions. My letter to a UK Health Minister, for example, led to an evidence synthesis on changing behaviour to increase healthy life expectancy.
- Build coalitions for regulation. Connect with organisations advocating for evidence-based policies on tobacco, alcohol, food, and transport. Collective advocacy is essential for countering industry influence. Look for opportunities to provide evidence summaries that support stronger regulation, similar to how tobacco control succeeded through coordinated expert engagement with policymakers.
