Diet

Our research on diet

We study how our environments influence what we eat, and which interventions could change this so that our diets can be healthier.

Click on the images below to find out more about the work we have been doing in this area:

 

Key Studies:

  • Does increasing the proportion of healthier options in cafeterias lead to healthier purchasing?

    Increasing the proportion of healthier foods available could encourage healthier consumption, but evidence to date is limited in scope and quality. In this study, six English worksite cafeterias increased the proportion of healthier cooked meals, snacks, cold drinks and/or sandwiches available, while aiming to keep the total number of food options constant. Healthier options were defined as those with fewer calories (kcal). When sites offered these changed food options, we found a 7% reduction in calories (kcal) purchased from targeted food categories across all the worksites. However, impact varied across sites, with calories purchased from targeted categories significantly reduced in two sites, but no significant differences observed in the other four sites. No difference was observed in the revenue taken by the worksites when healthier options increased. Overall, increasing the proportion of lower calorie options available in worksite cafeterias seems a promising intervention for healthier consumption. The reasons why this effect was found in some but not all the worksite cafeterias needs further study.

    Impact of increasing the proportion of healthier foods available on energy purchased in worksite cafeterias: A stepped wedge randomized controlled pilot trial. Pechey, R., Cartwright, E., Pilling, M., Hollands, G. J., Vasiljevic, M., Jebb, S. A., & Marteau, T. M. Appetite.

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  • What is the potential impact of calorie labelling in worksite cafeterias? A pilot study

    Reducing excess consumption of food and drink is core to tackling the high prevalence of overweight and obesity in the UK and elsewhere. Here we provide the results of a pilot trial estimating the potential impact of calorie labelling on energy purchased across six worksite cafeterias.

    Post-intervention feedback amongst cafeteria patrons and worksite managers and caterers suggested high levels of acceptability. Several barriers to intervention implementation were identified. The predicted effect of labelling to reduce energy purchased was only evident at one out of six sites studied. Before progressing to a full trial, we propose that the calorie labelling intervention needs to be optimised, and a number of operational issues resolved.

    Impact of calorie labelling in worksite cafeterias: a stepped wedge randomised controlled pilot trial. Vasiljevic M, Cartwright E, Pilling M, Lee M-M, Bignardi G, Pechey R, Hollands GJ, Jebb SA, Marteau TM, 2018

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  • Taxing sweet snacks may bring even greater health benefits than taxing sugar-sweetened drinks

    The UK Government levy on sugary drinks producers started in April 2018. This will potentially influence the cost of a large range of non-alcoholic beverages. Our new study (published 26th April 2018) looks at how increasing the price of snack foods might compare in impact. We found that a 10% increase in the price of sweet snacks could lead to a similar reduction in consumer demand as the same price increase for sugar-sweetened drinks. However, such a price increase is estimated to have knock-on effects that may further reduce purchases of sugar-sweetened drinks and other snacks. Furthermore, as sweet snacks provide twice as much sugar in the diet as sugar-sweetened drinks, the overall reduction on sugar intake could be even greater than that observed with price increases for sugar-sweetened drinks.

    Are sweet snacks more sensitive to price increases than sugar-sweetened beverages: analysis of British food purchase data. (2018). Smith RD, Cornelsen L, Quirmbach D, Jebb SA, Marteau TM. BMJ open.

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  • How do consumers perceive smaller vs. larger bottles of sugary drinks?

    Sixteen consumers of sugary drinks were interviewed about their experiences of using four different bottle sizes of cola: 1500 ml, 1000 ml, 500 ml, and 250 ml.

    Participants perceived their consumption pace and amount to be greater with the smallest (250ml) compared to larger bottles. The smallest bottles were described as increasing the frequency of drinking occasions and encouraging consumption of numerous bottles in succession.

    Various factors associated with the smallest bottles were described as enabling consumption, like the perceived convenience and portability and the greater number of smaller vs. larger bottles available. Further work is needed to experimentally test the use of small bottles as a method for decreasing sugary drink consumption.

    Perceived impact of smaller compared with larger-sized bottles of sugar-sweetened beverages on consumption: a qualitative analysis. Mantzari, Hollands, Pechey, Jebb & Marteau, 2017

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  • Can interventions in workplace cafeterias modify employees’ diets?

    Reducing excessive consumption of food and soft drinks is core to tackling the high rates of overweight and obesity in the UK and elsewhere. It is estimated that about one third of our daily energy intake is consumed while at work, with most of the food consumed not brought from home.

    This is a protocol for a pilot stepped wedge randomised controlled trial to estimate the potential impact of three sets of physical micro-environment interventions to reduce energy purchased in workplace cafeterias: 1) size of portions, packages and tableware; 2) availability of healthier vs. less healthy options; and 3) energy labelling.

    The results of this pilot study will inform the design and procedures for a larger trial.

    Physical micro-environment interventions for healthier eating in the workplace: protocol for a stepped wedge randomised controlled pilot trial. Vasiljevic, Cartwright, Pechey, Hollands, Couturier, Jebb & Marteau, 2017.

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  • Does bottle size affect the amount of cola consumed at home?

    We assessed the feasibility of running a trial on the impact of bottle size on in-home consumption of cola, in which households received a set amount of cola each week for four weeks, in bottles of one of four sizes (1500 ml, 1000 ml, 500 ml, or 250 ml). 16 households were tested and we found the procedures to be both feasible and acceptable.

    Issues associated with the study design were identified, which may impact the validity of the primary outcome (consumption). These include consumption driven by study-determined supply and a failure to capture out-of-home consumption. Methods to avoid these would be needed before conducting a definitive trial.

    Impact of bottle size on in-home consumption of sugar-sweetened beverages: a feasibility and acceptability study. Mantzari, Hollands, Pechey, Jebb & Marteau, 2017.

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  • Does presenting images of negative health outcomes lead to healthier food choices?

    Composite for BHRU websiteWe examined the impact on people’s choices of presenting food images paired with positive or negative images of the health consequences of eating those foods.

    Presenting images of negative health outcomes led to more healthy food choices, irrespective of whether they were paired with images of energy-dense snack foods or of fruit. Images of positive health outcomes did not alter food choices.

    This work provides insights relevant to health communication interventions where aversive visual images are used to alter the consumption of products that impact on human health.

    Pairing images of unhealthy and healthy foods with images of negative and positive health consequences: impact on attitudes and food choice. Hollands & Marteau. 2016

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  • Is acting on intentions to change diet socially patterned?

    Bringing together data from previous studies, we found no evidence that those from more deprived groups are less likely to act on their intentions to change their behaviour, including changing their diet.

    However, we found some differences between more and less deprived groups in terms of the influence of perceived control over behaviour (self-efficacy) on actual behaviour:

    • for those from less deprived groups, higher perceived control over their behaviour was associated with healthier behaviour;
    • for those from more deprived groups, perceived control over behaviour had no relation to health behaviour.

     

    This suggests interventions that do not require active engagement from people may be more effective at reducing health inequalities, as responses to these may be less likely to depend on attributes like perceived control over behaviour.

    Is the intention–behaviour gap greater amongst the more deprived? A meta-analysis of five studies on physical activity, diet, and medication adherence in smoking cessation. Vasiljevic, Ng, Griffin, Sutton & Marteau. 2016.

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  • What are the policy options to “Downsize” portions, packages and tableware?

    BMJ-infographic_portions_v5In this paper we outline a range of actions with the potential to avoid the excess consumption of food and drink that consistently occurs when people are presented with larger portions, packages and tableware size.

    The actions focus on reducing the size, availability and appeal of such larger sized portions, packages and tableware.
    The analysis considers: what interventions might work; where these interventions can be made; how they might be achieved; and who needs to act to enable the changes. This builds on our recent Cochrane Portion Size review.
     

    Downsizing: policy options to reduce portion sizes to help tackle obesity. Marteau, Hollands, Shemilt & Jebb. 2015.

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  • Can portion, package and tableware size increase consumption?

    shutterstock_41447758.jpgOur systematic review has produced the most conclusive evidence to date that people consistently consume more food and drink when offered larger-sized portions, packages or tableware than when offered smaller-sized versions.

    The size of this effect, based on combining data from 61 randomised controlled trials (6,711 participants), suggests that if sustained reductions in exposure to large sizes could be achieved across the whole diet, this could reduce average daily energy consumed from food by up to 16% (279 kcals) among UK adults.

     

    Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco. Hollands, Shemilt, Marteau, Jebb, Lewis, Wei, Higgins & Ogilvie. 2015.

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    • To view Cochrane UK coverage of this Cochrane review in the ‘Evidently Cochrane’ blog (from 15/09), click here.
    • To join the Twitter conversation about this Cochrane review, follow: @BHRUCambridge and #PortionSize

     

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Publications related to diet:

2019

2018

2017

2016

2015

2014

2013

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