Unconscious consumption: is our environment making us eat more?

A pile of plates and dishes

Elizabeth CastleElizabeth Castle works as a Behavioural Insights Research Analyst for Public Health England’s Behavioural Insights Team where she is leading on several randomised control trials to test the application of behavioural insights to public health policy.



Karen TanKaren Tan is a Behavioural Insights Researcher in Public Health England’s Behavioural Insights team. She leads on a portfolio of qualitative and quantitative research, including randomized control trials, to improve the development and implementation of the NHS Health Check programme.

The new year is often a time for making healthy changes – to drink or eat less, or get down to the gym more often. All of these things are important to maintain a healthy weight, but being aware of the environment around us can also help to make sure that healthy eating and sensible portions become the norm, not just a yearly resolution.

Being overweight or obese is the most important avoidable cause of cancer after smoking. World Cancer Research Fund International’s analysis of global research shows strong evidence that overweight and obesity lead to an increased risk of 10 cancers. Reducing obesity is, therefore, paramount in the fight against cancer, but what can be done? This blog explores the latest evidence from behavioural science literature on tackling obesity by appealing to our unconscious, or automatic, motivation.

The automatic system & decision making

Nobel Prize-winning psychologist and behavioural economist Daniel Kahnenman wrote extensively about how our behaviour is driven by two processes: a slow, conscious, analytical system and a fast, automatic, intuitive system.

Although many of us like to consider ourselves rational individuals, a large proportion of our behaviour is driven by unconscious automatic processes. This makes us particularly vulnerable to subtle physical and social cues in our environments that can cause us to behave unhealthily.

The power of physical environmental cues

recent Cochrane Review, assessing 61 studies, found that portion size significantly increases how much we unconsciously eat, making it a key contributor to the high prevalence of obesity in the UK and internationally. Our idea of a reasonable portion size often comes down to the size of say, a packet of crisps or a bottle of cola. However, the assumption that a packaged product is a suitable portion size might be wrong, even if the label says ‘single serving’, and research suggests that the size of packaged food is increasing.

More generally, cues to an appropriate portion size are not always obvious. The size of our plate, for example, can indicate to us how much food we should serve ourselves and can alter our perception of acceptable portion sizes. In one study, individuals who were provided with larger bowls served and ate 16% more cereal than those with smaller bowls.

Perhaps more worryingly, when asked to estimate how much they had eaten, the individuals with the larger bowls thought that, on average, they had eaten 7% less than those with the smaller bowls! Using a smaller plate or bowl gives us the impression that we are eating more, and can leave us more satisfied than if we eat the same amount of food from larger tableware.

The power of social environmental cues

Similarly, social cues can also determine not just what types of food and drink we consume, but also how much. A recent review of the effect of social facilitation on consumption – how we behave with others compared with being alone – found that as the number of people we eat with increases, so does the amount of food we consume.

In one study, for example, eating with one other person was found to increase consumption by 33%, eating with three people by 53% and eating with six people by 76%. Research has found that, in the presence of familiar company, we tend to select more food and drink than if we had been dining alone. It is suggested that an implicit social agreement exists between diners that provides justification for eating more than we otherwise would.

In social situations we observe the food and drink choices of others and use these observations as cues to the socially acceptable portion size. We often use the behaviour of others to license ourselves to select more food than we normally would.

Some behavioural science tips for healthy consumption

So how do we combat these physical and social cues? Mindless eating is often driven by the environment that we are in, which ‘nudges’ us to eat and drink more than we intend to consume. Public Health England is actively tackling environments that encourage unhealthy eating by highlighting portion size reduction as one part of several actions to lessen the harmful effects of high sugar intake.

Within the Public Health England Behavioural Insights Team, we are building a portfolio of research that applies behavioural science to several food environments with the shared objective to improve the food and drink choices made in these places.

Of course, we can also make healthier changes by ourselves and, broadly, we have two options to do so. Firstly, we can train our rational, reflective system to be more aware of the effect of environmental cues on our consumption and actively resist temptations. This approach is, however, difficult, time consuming and prone to error.

Alternatively, we can make changes to our environments which work with our automatic system, such as, eating from smaller plates or dividing large packets of food into smaller healthy sized portions. Making such changes to your environment can encourage healthier consumption without relying so heavily on cognitive control and willpower, increasing the sustainability and likelihood of making better healthier choices.