Adding nutritional labels to menus and next to food in restaurants, coffee shops and cafeterias may reduce calorie consumption, according to new research involving the University of Stirling.
Eating too many calories contributes to people becoming overweight and increases the risks of heart disease, diabetes and many cancers, which are among the leading causes of poor health and premature death.
Several studies have looked at whether putting nutritional labels on food and non-alcoholic drinks might have an impact on their purchasing or consumption, but findings have been mixed.
Dr Rachel Crockett, of Stirling's Faculty of Natural Sciences, said the study would be a key resource for policymakers.
Now, a team of Cochrane researchers has brought together the results of studies, evaluating the effects of nutritional labels on purchasing and consumption habits, in a systematic review.
The team – including Dr Rachel Crockett, a Lecturer in Psychology at Stirling – reviewed the evidence to establish whether, and by how much, nutritional labels on food or non-alcoholic drinks affect the amount of food or drink people choose, buy, eat or drink.
Researchers considered studies in which the labels had to include information on the nutritional or calorie content of the food or drink. They excluded those including only logos, such as ticks or stars, or interpretative colours, for example ‘traffic light’ labelling, to indicate healthier and unhealthier foods.
In total, the researchers included evidence from 28 studies, of which 11 assessed the impact of nutritional labelling on purchasing and 17 assessed the impact of labelling on consumption.
The team combined results from three studies where calorie labels were added to menus or placed next to food in restaurants, coffee shops and cafeterias. For a typical lunch with an intake of 600 calories, such as a slice of pizza and a soft drink, labelling may reduce the energy content of food purchased by about eight per cent (48 calories). The authors judged the studies to have potential flaws that could have biased the results.
Combining results from eight studies carried out in artificial or laboratory settings could not show with certainty whether adding labels would have an impact on calories consumed. However, when the studies with potential flaws in their methods were removed, the three remaining studies showed that such labels could reduce calories consumed by about 12 per cent a meal.
The team noted that there was still some uncertainty around this effect and that further studies are required to establish the size of the effect with more precision.
The Review’s lead author, Professor Theresa Marteau, Director of the Behaviour and Health Research Unit at the University of Cambridge, said: 'This evidence suggests that using nutritional labelling could help reduce calorie intake and make a useful impact as part of a wider set of measures aimed at tackling obesity.'
'There is no ‘magic bullet’ to solve the obesity problem, so while calorie labelling may help, other measures to reduce calorie intake are also needed.'
Dr Crockett, of the Faculty of Natural Sciences, said: 'This comprehensive review of the research on the impact of nutritional labelling on food purchasing and consumption shows small, but important, beneficial effects. This evidence will be important to health policymakers in Scotland as they develop strategies to tackle high rates of obesity.'
The researchers were unable to reach firm conclusions about the effect of labelling on calories purchased from grocery stores or vending machines because of the limited evidence available. They also added that future research would also benefit from a more diverse consideration of the possible wider impacts of nutritional labelling including impacts on those producing and selling food, as well as consumers.
Professor Ian Caterson, President of the World Obesity Federation, said: 'Energy labelling has been shown to be effective: people see it and read it and there is a resulting decrease in calories purchased. This is very useful to know – combined with a suite of other interventions, such changes will help slow and eventually turnaround the continuing rise in body weight.'
The study also involved Sarah King, Giacomo Bignardi and Gareth Hollands (all of the University of Cambridge), Toby Prevost (Imperial College London), Nia Roberts (University of Oxford) and Brendon Stubbs (Kings College London).
The research, Nutritional labelling for healthier food or non-alcoholic drink purchasing and consumption, is published in the Cochrane Database of Systematic Reviews 2018.