Using psychology to get people eating more fruit

Do you eat a piece of fruit on the way to work or school everyday without even thinking about it? Perhaps that is the full extent of your fruit eating? If so you're just the kind of person who won't be helped by public health information campaigns seeking to increase our fruit eating. That's according to a new study that suggests people who already eat fruit (though not enough) habitually are more likely to benefit from interventions that make fruit more easily available.

A dominant theory in health psychology is the Theory of Planned Behaviour, which states that our attitudes, our perception of social norms and our sense of control all impact on our intentions to perform a given health behaviour, and therefore the likelihood we will perform that behaviour.

Gert-Jan de Bruijn and colleagues applied this theory to the fruit eating tendencies of 521 participants, but unlike most prior research, they added in a measure of habit – that is, whether the participants said they often ate fruit automatically, without thinking about it.

Consistent with the Theory of Planned Behaviour, the Dutch psychologists found that among the participants who had either a weak or medium fruit-eating habit, their self-reported intentions to eat fruit were predictive of their fruit consumption measured five weeks later.

Crucially, however, this wasn't true for the participants who had a strong fruit-eating habit. The strongest predictor of their subsequent fruit consumption wasn't their prior intentions, but their sense of how easy it would be to eat fruit.

This has practical implications. The idea behind public health information campaigns is that they increase our intention to perform a given behaviour, via our attitudes, sense of social norms and feelings of control. However, if intentions are unrelated to future fruit eating in people who already eat fruit (though not enough) habitually, then information campaigns are unlikely to change their behaviour.

"Consequently, health behavioural change for those with strong habits may be more dependent on environmental manipulations – making healthy foods more readily available," the researchers said.

Further reading

De Bruijn, G-J., Kremers, S.P.J., De Vet, E., De Nooijer, J., Van Mechelen, W. & Brug, J. (In press). Does habit strength moderate the intention-behaviour relationship in the Theory of Planned Behaviour? The case of fruit consumption. Psychology and Health.