Introduction

The consumption of sugar-sweetened beverages has been suggested as a contributory factor to the rising levels of childhood obesity in many countries worldwide. Recent systematic reviews of the literature confirm the link between increased intake of free sugars, particularly in the form of sugar-sweetened beverages and unhealthy weight gain in both children and adults (1, 2) while reducing consumption of sugar-sweetened beverages has been shown to reduce weight gain in children, particularly in those who are already overweight (2–4). This commentary will focus on results from two recent systematic reviews of impact of sugar-sweetened beverage consumption on childhood overweight and obesity (1, 2).

Methodology summary

The systematic review and meta-analysis by Te Morenga et al. was conducted according to the methods of the Cochrane collaboration (5). Malik et al. used standard methods for conducting and reporting meta-analyses. Both reviews included randomised controlled trials (RCTs) and prospective cohort studies conducted in children or adults, which were identified by searching the literature in numerous databases including PubMed, Embase and The Cochrane library. Bias in the RCTs was assessed using the Cochrane Collaboration’s risk of bias tool and Malik et al. used the Newcastle Ottawa scale to assess bias in the cohort studies. Te Morenga et al. further assessed quality of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology (6).

Evidence summary

Twenty-one cohort studies were identified in the Te Morenga et al. study (1) assessing the effect of an increase in free sugars intake on measures of body fatness in children; results from meta-analysis of five of these studies show a significant association between sugar-sweetened beverage consumption and the prevalence of overweight after a one year follow-up period, with a 55% increased likelihood of children being overweight or obese at follow-up if they consumed one or more servings of sugar-sweetened beverages per day at baseline, compared with children who consumed none or very little at baseline (odds ratio [OR] 1.55, [95%CI: 1.32 to 1.82]; p<0.001). Meta-analysis of five intervention trials assessing the effect of a reduction in free sugars intake on measures of body fatness in children found that compared to no intervention, interventions which advised children to consume less free sugars or fewer sugar-sweetened beverages generally had no significant impact on body mass index (BMI; kg/m2) (standard mean difference (SMD) 0.09 [95%CI: –0.14 to 0.32]; p=0.45), though it was observed that overall compliance to the dietary advice was low in most trials.

Fifteen cohort studies consisting of 25,475 children were included in the meta-analysis by Malik et al. (2), assessing the effect on BMI of sugar sweetened beverage consumption. Results indicate that body mass index (BMI) increased by 0.07 (95%CI: 0.01 to 0.12) for each additional daily 12 ounce serving of sugar-sweetened beverage over the duration specified in each study. Additionally, meta-analysis of seven cohort studies including 15,736 children show that BMI increased by 0.06 (95%CI: 0.02 to 0.10) for each additional daily 12 ounce serving of sugar-sweetened beverage over a 1-year period. Meta-analysis of five RCTs including 2,772 children found a non-significant association between reduced consumption of sugar-sweetened beverages and BMI (weighted mean difference –0.17 [95%CI: –0.39 to 0.05]. Subgroup analysis showed a significant decrease in BMI (SMD –0.34 [95%CI: –0.50 to –0.18]) in three studies that provided noncaloric beverages as substitutes for sugar-sweetened beverages. No significant difference in BMI was observed in two studies that focused on school-based education (SMD 0.01 [95%CI: –0.19 to 0.20]).

Discussion

The evidence for a link between sugar-sweetened beverage consumption and childhood obesity is compelling. Further evidence continues to emerge, with two papers published in 2012 showing that interventions to reduce consumption of sugar-sweetened beverages significantly decreased weight gain in children and adolescents (3–4). In one of the papers, the researchers found that a reduction of 104 kcal from sugar-sweetened beverages per day (about 70% of a standard 330 ml portion) was associated with 1.01 kg less weight gain over 1.5 years among normal weight children (3).

The weight of evidence has been sufficient for many scientific associations and expert bodies to recommend the reduction in free sugars intake, in particular the consumption of sugar-sweetened beverages as a public health policy goal. These include the American Medical Association, the US Institute of Medicine of the National Academies, the US Centers for Disease Control, and the World Health Organization’s expert reports (7, 8). To these reports may be added the recommendations given in many national food-based dietary guidelines to limit the consumption of free sugars and sugar-sweetened beverages.

Relevance to under-resourced settings

While sales of sugar-sweetened beverages have been relatively static or declining in many high-income countries in recent years, they are typically increasing at 3% per annum globally (9), with much of the increase in low-and middle-income countries in Asia and Latin America: India reports 7% annual increases in sales (10) and Brazil 6% (11).

Per capita consumption in low-and middle-income countries shows the potential for growth: data for 2012 from the leading manufacturer, Coca-Cola, show the world average consumption levels of their beverage products to be 94 portions per person per year. Levels in many low-and middle-income countries are currently much lower, at 14 portions per person per year in India, 16 in Indonesia, 21 portions in Pakistan, and 39 in Kenya and China. In countries with more developed economies, consumption levels are higher: 65 portions per person per year in Egypt, 79 in Russia, 99 in South Korea, 113 in Thailand and 131 in the Philippines. The market for soft drinks is highest in Central and South America: 219 portions per person per year in Peru, 263 in Bolivia, 416 in Panama, 486 in Chile, and 745 in Mexico, the world leader (12).

Evidence on the quantities being consumed by children and young people is available in surveys such as the Health Behaviour in School-aged Children (HBSC) survey (13) and the Global school-based student health survey (GSHS) (14). Although the data are from questionnaires filled in by the students, and should be validated against measured survey data, the figures can be indicative of relative differences in behaviour. The table below gives examples of consumption levels of carbonated soft drinks, reported by adolescents aged 13–15 years.

Proportion of adolescents 13–15 years drinking one or more servings of carbonated soft drinks daily

Implementation of interventions

As discussed above, direct interventions to reduce consumption of sugar-sweetened beverages in school children, e.g. through health education in school settings, has achieved only limited effects, and their sustainability is not known. Other forms of intervention, which directly aim to affect the availability and marketing of the products at various stages in the supply chain, may be more effective, and some can affect consumption across an entire population. Examples include:

• replacement of sugar-sweetened beverages in school vending machines with bottled water;
• school rules to restrict sugar-sweetened beverages in classrooms, canteens and lunchboxes;
• provision of fresh drinking water fountains in schools and other locations where children gather;
• imposition of taxes or levies on sugar-sweetened beverages;
• requirements for all advertisements for sugar-sweetened beverages to include health promotion messages; and
• restrictions on the advertising of sugar-sweetened beverages (in general, or targeted at children or aired during children’s television programming).

In May 2010, the Sixty-third World Health Assembly adopted resolutionWHA63.14, which supports a set of recommendations to limit children’s exposure to the marketing of sugar-sweetened beverages, along with other products high in fats, sugars and salt. Several large, multi-national manufacturers have voluntarily moved to restrict their marketing to children. Coca-Cola stated “We do not market any products directly to children under 12. This means we will not buy advertising directly targeted at audiences that are more than 35% children under 12. Our policy applies to television, radio, and print, and, where data is available, to the Internet and mobile phones" (15). The world’s second largest soft drink manufacturer, PepsiCo, stated that the company will “advertise to children under the age of 12 only products that meet specific nutrition criteria. ... In 2010, we announced strict science-based criteria that ensure only our most nutritious products meet the standard for advertising to children under the age of 12" (16).

It should be noted that these voluntary measures still permit advertising in media seen by children, e.g. family TV programming and social digital media to which children gain access. Social media are a relatively low-cost platform for brand enhancement and are used for successful communication directly to children: Coca-Cola is ranked sixth in the most popular Facebook pages globally (September 2013), and is the only food and beverage brand in the top 40, with 72 million Facebook fans and 1.7 million Twitter followers (17). Social media are used extensively by children under 12 years of age and are relatively difficult for parents to monitor or control.

A systematic review of children’s exposure to food and beverage marketing messages found consistent evidence that exposure had continued at high levels in recent years (2007–2012), despite evidence from industry funded reports over the same period showing that the companies were adhering to their self-regulatory guidelines (18). The review concluded that the self-regulatory criteria were not sufficient to ensure children were protected from the advertising of foods and beverages high in fats, sugars and salt and that government-led criteria for restricting marketing would be preferable.

References

1. Te Morenga L, Mallard S, Mann J. Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ. 2013; 346:e7492.

2. Malik VS, Pan A, Willett WC, Hu FB. Sugar-sweetened beverages and weight gain in children and adults: a systematic review and meta-analysis. American Journal of Clinical Nutrition. 2013; 98(4):1084-102.

3. de Ruyter JC, Olthof MR, Seidell JC, Katan MB. A trial of sugar-free or sugar-sweetened beverages and body weight in children. New England Journal of Medicine. 2012; 367(15):1397-406.

4. Ebbeling CB, Feldman HA, Chomitz VR, Antonelli TA, Gortmaker SL, Osganian SK, Ludwig DS. A randomized trial of sugar-sweetened beverages and adolescent body weight. New England Journal of Medicine. 2012; 367(15):1407-16.

5. Higgins JPT, Green S. Cochrane Handbook for systematic reviews of interventions version 5.0.2. www.cochrane-handbook.org.

6. Guyatt GH, Oxman AD, Vist GE, Kunz R, Falck-Ytter Y, Alonso-Coello P, et al. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ. 2008;336:924-6.

7. WHO. Diet, nutrition, and the prevention of chronic diseases. Report of a WHO Study Group meeting held in Geneva from 6-13 March 1989 (WHO Technical Report Series 797). Geneva: World Health Organization; 1990.

8. WHO. Diet, nutrition and the prevention of chronic diseases. Report of a joint WHO/FAO expert consultation, 28 January - 1 February 2002, Geneva, Switzerland (WHO Technical Report Series 916). Geneva: World Health Organization; 2003.

9. Global Soft Drinks [online document]. London: MarketLine; 2013. (http://marketpublishers.com/report/consumers_goods/food_beverage/global_soft_drinks.html, accessed 1 September 2013).

10. Soft Drink Industry in India [online information service]. New Delhi: NIIR Project Consultancy Services; 2012 (http://www.niir.org/information/content.phtml?content=184, accessed 1 September 2013).

11. Brazil – Soft drinks. Industry Profile [online document]. London: MarketLine; 2013( http://www.datamonitor.com/store/Product/brazil_soft_drinks?productid=MLIP0929-0005, accessed 1 September 2013).

12. Coca-Cola: 2012 Year in Review Online [online document]. Atlanta GA: The Coca-Cola Company; 2012 (http://www.coca-colacompany.com/annual-review/2012/pdf/TCCC_2012_Annual_Review.pdf, accessed 1 September 2013).

13. Currie C et al. (eds). Social determinants of health and well-being among young people. Health Behaviour in School-aged Children (HBSC) study: International report from the 2009/2010 survey. Health Policy for Children and Adolescents, No. 6. Copenhagen. Copenhagen: WHO Regional Office for Europe; 2012.

14. WHO. Global school-based student health survey [online database]. Geneva: World Health Organization; 2013 (http://www.who.int/chp/gshs/en/, accessed 1 September 2013).

15. Coca-Cola. Responsible Marketing [online statement]. Atlanta GA: The Coca-Cola Company; 2012 (http://www.coca-colacompany.com/stories/responsible-marketing, accessed 1 September 2013).

16. PepsiCo, Inc. Responsible Marketing & Advertising [online statement]. Purchase NY: PepsiCo; 2012 ( http://www.pepsico.com/Purpose/Human-Sustainability/Responsible-Marketing.html, accessed 1 September 2013).

17. Fanpagelist. Top Facebook Fan Pages [online database]. 2013; (http://fanpagelist.com/, accessed 1 September 2013).

21. Galbraith-Emami S, Lobstein T. The impact of initiatives to limit the advertising of food and beverage products to children: a systematic review. Obesity Reviews. 2013; 14(12):960–974.

Disclaimer

The named authors alone are responsible for the views expressed in this document.

Declarations of interests

Conflict of interest statements were collected from all named authors and no conflicts were identified.