Younger and less educated people were less likely to choose fruit after watching the adverts, as well as being less likely in general to equate fruit as being a tasty snack.
The study, led by Suzanna Forwood of Cambridge University, used mock television adverts and questionnaires with banners bearing positive words as primes in an attempt to mimic the real-world stimuli that consumers are exposed to, such as television adverts and slogans on food packaging.
Priming is a psychological effect relying on memory whereby exposure to one stimulus will increase the responsiveness to another without raising conscious awareness of a link between the two.
The researchers said the study could have implications for policy makers since the adverts promoting healthy eating had little effect on those in lower socio-economic groups, who already had a low fruit and vegetable intake.
“Adopting primes such as those explored in the current study as a population-wide intervention could therefore widen a pre-existing social inequality in fruit and vegetable intake,” the study said.
A total of 907 randomly selected subjects participated in the two-part study, with the first part assessing the impact of hunger on snack choices and the second looking specifically at education levels.
Subjects viewed an advert for fruit and vegetables or, as a control, no advertisement, and were then asked which they would prefer to eat among seven pieces of fruit and seven sweet dairy or pastry snacks.
Among other tasks, they were asked “Which is the most important for you when choosing what food to eat?” and given a choice of ‘health’, ‘cost’, ‘taste’, ‘weight control’ and ‘convenience.’ Subjects also placed a set of words – including ‘natural’, ‘wholesome’, ‘nutritious’ and ‘yummy’, ‘tasty’, ‘appetising’ – into one of two categories, ‘fruit’ or ‘pastry/snack’.
The researchers found that hunger reduced preferences for fruit overall, while more educated participants – according to their level of academic qualifications – chose more fruit when hungry and primed.
Less educated participant preference for fruit was unaffected by either hunger or the prime.
Positive or negative?
Suzanna Forwood, who led the study, said: “Our objective was to see whether these general interventions [healthy eating adverts] would be effective across the whole population, and we found that this was not the case. So as it stands they would not be very effective for health policy makers.”
Malcolm Clarke of the Children's Food Campaign, however, said that the study’s findings should be viewed positively as the adverts were partially effective.
“The mock adverts served to reinforce a positive message to those who already eat fruit while having no negative consequences on others.”
“This shows that a twin-approach is needed, with measures that discourage junk food whilst making healthy food affordable and available to people from all socio-economic backgrounds.”
The scientists have called for more research before using advertising to promote healthy eating.
“Our findings ring true with those who have an understanding of marketing campaigns – you have to target specific sectors,” Forwood said.
Vol 89, pp 93–102, doi: 10.1016/j.appet.2015.01.018
Title: “Priming healthy eating. You can't prime all the people all of the time.”
Authors: Forwood SE, Ahern AL, Hollands GJ, Ng YL, Marteau TM.