This is a plain English summary of an original research article
This Cochrane review found that people ate and drank more when offered larger-sized portions or when using larger tableware (such as plates, bowls, bottles or glasses). However, the evidence for the effects of portion, package and tableware size on selection and consumption was of moderate quality and most of the included studies (58 of 72) were conducted in the US. The implications for commissioning and public health practice will require judgment and local knowledge.
The increase in consumption was about 215 to 279 kcal or 12 to 16% of the average energy intake for a UK adult. Adults increased their intake about twice as much as children. The findings re-enforce NICE guidance, which recommends encouraging people to limit their portion size.
The results also support public health programmes that try to reduce food or drink intake by including advice on portion size. No research on the portion size of alcoholic (as opposed to non-alcoholic) drink consumption was found.
Why was this study needed?
Overeating, drinking too much alcohol and smoking have all been shown to increase the risk of cancers, heart disease, diabetes and various other non-communicable diseases. For example, an obese woman is 13 times more likely to develop type 2 diabetes. These diseases reduce quality of life and increase healthcare costs. Although the rate of smoking is gradually reducing in the UK, the rate of obesity is rising rapidly. The Health and Social Care Information Centre report that obesity rates have increased for men from 13.2% in 1993 to 26% in 2013 and from 16.4 to 23.8% for women.
People are repeatedly exposed to varying shapes and sizes of food, alcohol and tobacco products in shops, restaurants and bars. This review aimed to see how influential product size and shape is on our choices and consumption in order to inform health promotion interventions to reduce obesity, alcohol-related illness and smoking rates.
What did this study do?
This Cochrane systematic review and meta-analysis found 72 eligible randomised controlled trials. They compared at least two groups of people presented with a choice of size or shape of a portion, package or item of tableware, on their selection or consumption of food, alcohol or tobacco products. Sixty nine studies looked at food and non-alcoholic drinks and three at tobacco products; no studies on alcoholic drinks were found. Almost all of the studies assessed responses to different sizes rather than shapes.
The average age of participants ranged from three to 55 years, with more studies in adults than children.
The methods used for the review were sound and the researchers assessed the risk of eleven types of bias in the included studies. There was an unclear risk of bias in over 75% of studies reporting the consumption outcome and in 43 studies there were differences in the baseline characteristics between the comparison groups that themselves could have led to differences in outcome, independent of the intervention. Two of 72 included trials were from the UK whereas the majority were conducted in the USA, where portion sizes may be larger than in the UK. Therefore, these results need to be treated with some caution.
What did it find?
- People consistently ate more food or drank more non-alcoholic drinks when offered larger-sized portions, packages or items of tableware than when offered smaller-sized versions. The effect was considered small to moderate, equivalent to about 215 to 279 kcal or 12 to 16% of average energy intake for a UK adult (Standardised Mean Difference [SMD] 0.38, 95% Confidence Interval [CI] 0.29 to 0.46). This came from a meta-analysis of 58 studies, 6603 participants.
- The effect of portion size was greater (about double) amongst adults than children.
- People selected more non-alcoholic drinks when they were offered them in shorter and wider glasses or bottles, compared to taller and narrower vessels. The effect was considered very large (SMD 1.47, 95% CI 0.52 to 2.43), but came from a meta-analysis of just three very diverse studies.
- There was no difference when comparing longer and shorter cigarettes.
What does current guidance say on this issue?
NICE guidance, published in 2015, targeted at everyone who provides information on weight management, recommends encouraging people to choose smaller portions and avoid additional servings.
What are the implications?
At face value, the results suggest that policies and practices that reduce the size, availability and appeal of larger-sized portions, packages and tableware will reduce the amount people eat and drink. However better quality underlying research is required and despite the intuitively attractive conclusions, balanced policies in the complex area of obesity prevention will need more than one review. Potential interventions that could be tested further include education, changes to regulatory and legislative frameworks, voluntary agreements with the food industry, reducing default serving sizes of energy-dense food, or providing smaller crockery, cutlery and glasses in food outlets.
There was not enough evidence on whether the effect size varied between people from different socioeconomic groups, so it remains uncertain whether any successful interventions would reduce health inequalities. There was also not enough evidence to guide policy or practice on tobacco or alcohol “portion” or packet size.
Hollands GJ, Shemilt I, Marteau TM, et al. Portion, package or tableware size for changing selection and consumption of food, alcohol and tobacco. Cochrane Database Syst Rev. 2015;9:CD011045.
C3 Collaborating for Health. Non-communicable diseases in the UK. A briefing paper prepared for the UK Parliament (House of Lords). London: C3 Collaborating for Health; 2011.
Health and Social Care Information Centre. Statistics on Obesity, Physical Activity and Diet. England 2015. Leeds: Health and Social Care Information Centre; 2015.
Health and Social Care Information Centre. Statistics on Smoking. England 2015. Leeds: Health and Social Care Information Centre; 2015.
NICE. Maintaining a healthy weight and preventing excess weight gain among adults and children. NG7. London: National Institute for Health and Care Excellence; 2015.
Marteau TM, Hollands GJ, Shemilt I, et al. Downsizing: policy options to reduce portion sizes to help tackle obesity. BMJ. 2015; 351: h5863.
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