Paper

International Journal of Obesity (2005) 29, S54–S57. doi:10.1038/sj.ijo.0803062

Prevention of childhood obesity by reducing soft drinks

J James1 and D Kerr1

1Bournemouth Diabetes and Endocrine Centre, Royal Bournemouth Hospital, Castle Lane East, Bournemouth, UK

Correspondence: J James, Bournemouth Diabetes and Endocrine Centre, Royal Bournemouth Hospital, Castle Lane East, Bournemouth BH7 7DW, UK. E-mail: janet.james@rbch.nhs.uk

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Abstract

Aims:

 

The increasing prevalence of childhood obesity is a global problem. There are a variety of environmental factors that may be contributing to this increase. One such factor may be the increased consumption of soft drinks.

Objective:

 

This review will describe some of the latest research that has examined the association between obesity and the consumption of soft drinks.

Results:

 

The association between the consumption of sugar-sweetened drinks and childhood obesity has been established in three separate American studies. It has been found that children who consume these drinks have a higher energy intake and are more likely to become overweight. In adult women, the consumption of sugar-sweetened soft drinks has been associated with an increased risk of developing diabetes. In the United Kingdom, a school-based initiative focusing on reducing the consumption of these drinks has also been effective in preventing a further increase in obesity.

Conclusions:

 

There is an association between obesity and consumption of soft drinks. Initiatives focusing on reducing the consumption of these drinks may help to prevent a further increase in childhood obesity.

Keywords:

childhood obesity, prevention, soft drinks, school-based intervention

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Introduction

Childhood obesity is a major public health issue. The prevalence has increased in both the industrialised and developing world. In Thailand, the prevalence among 6- to 12-year-old children increased from 12.2 to 15.5% over a 2-y period from 1991 to 1993.1 While a recent report suggested that one in four children in the United Kingdom are either overweight or obese.2 The prevalence of obesity among children aged 2 to 10 has increased from 9.9% in 1995 to 13.7% in 2003, with obesity levels similar in both genders.

There are marked differences in prevalence of the problem between varying countries. A recent study comparing prevalence among adolescents between 13 European countries and the United States found that Ireland, Greece, Portugal and the United States had the highest rates, while the Czech Republic, Denmark, Flemish Belgium, France, Germany, Lithuania and Sweden had significantly lower levels of overweight adolescents.3

Being overweight or obese in childhood can have devastating metabolic, physical, psychosocial and economic consequences, particularly if the child becomes an obese adult.4 Genetic or endocrine conditions are rarely implicated as the primary cause of childhood obesity and most children gain weight due to an imbalance between energy intake and expenditure.5

The current Western environment includes an abundance of palatable, relatively inexpensive, energy dense foods. Combined with this is often aggressive food marketing.6 One of the most notable environmental changes over the last few decades has been food availability and portion size. In addition, there is a trend for increased consumption of food outside the home environment, and these foods tend to be highly calorific.6 It is also commonplace to 'super size' fast food meals and drinks.7 The fast food industry has been an international success with one fast food chain claiming to having 30 000 restaurants in 119 countries and serving an average of 47 million customers each day.8

In 1997, the National Diet and Nutrition Survey reported on the diets of United Kingdom young people aged between 4 and 18 y.9 This highlighted a number of areas of concern; chocolate was consumed by more than 80% of children, 74% did not eat any citrus fruit and 58% did not eat any green leafy vegetables. Notably, the majority of young people consumed carbonated soft drinks, with the average weekly consumption 1500 ml for boys and 750 ml for girls.

The consumption of carbonated drinks has been implicated as a contributor to the obesity epidemic. In the United States, soft drink consumption has increased by 500% over the last 50 y10 and represents the largest single food source of calories in the US diet,11 often displacing other more nutritious drinks such as milk and fruit juice.12 There is further concern that high consumption of these drinks will lead to excessive energy intake. The average adjusted energy intake is 10% higher for children who regularly consume carbonated drinks compared to nonconsumers.12

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Methods

The consumption of soft drinks and its association with obesity has been highlighted in a number of recent research articles. The term soft drinks is used to include carbonated drinks and sugar-sweetened drinks. The results of these studies are described below.

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Results

Ludwig et al13 examined the relationship between the consumption of sugar-sweetened drinks and childhood obesity in 548 ethnically diverse children, over a period of 19 months. They reported that with each increased serving of sugar-sweetened carbonated drink, body mass index and frequency of obesity increased. The odds ratio of becoming obese increasing 1.6 times for each additional sugar-sweetened drink consumed each day.

A small longitudinal study was conducted over a summer camp and assessed sweetened drink consumption in 30 children aged 6–13 y.14 Although the results were not significant, the authors found that increased consumption of sweetened drinks was associated with a higher total daily energy intake. The children who consumed the most sweetened drinks had the highest energy intake and also gained the most weight over the summer camp.

Schulze et al15 used longitudinal data from the Nurses Health study II to examine the association between consumption of sugar-sweetened drinks, weight gain and risk of type II diabetes in women. This large study found that women who increased their sugar-sweetened soft drink consumption had also increased their total daily calorie intake, with most of the additional calories resulting from soft drinks. Women who consumed more than one soda a day had a significantly higher risk of developing diabetes than women who consumed less than one of these drinks a month.

Welsh et al16 conducted a large retrospective study in children aged 2 and 3, to assess for any association between obesity and consumption of sweet drinks in this younger age group. This study found that daily consumption of one or more sugar-sweetened drink increased the chance of overweight among children already at risk of overweight, and continued the likelihood of remaining overweight among children already established as overweight. This relationship remained the same for all sweetened drinks including sodas and other sugar-containing drinks. When only fruit juices were considered, there was no significant association for the children who were normal weight or at risk of becoming overweight, although for children already overweight, the association was diminished but the results remained significant.

The CHOPPS project (Christchurch Obesity Prevention Project in Schools) conducted in the United Kingdom was a cluster randomised controlled trial including 644 children. The aim of this project was to determine if a specific, school-based educational initiative focusing on reducing consumption of carbonated drinks would be effective in preventing weight gain in children aged 7–11 y old.17

The primary objective was to discourage consumption of a single 'unhealthy' substance (carbonated drinks) with positive affirmation of a balanced healthy diet. Each term, a 1-h session was assigned for each class over the school year (four terms). Teachers assisted in each session and were encouraged to reiterate the message in other lessons. Group projects, games and classroom discussion were used. The initial session focused on the 'balance of good health', and the promotion of water drinking in place of carbonated drinks. Fruit tasting was used to demonstrate natural healthy sweet-tasting products. In addition, each class was given a tooth immersed in a popular sweetened carbonated cola to assess the effects of these drinks on dentition. The second and third sessions involved a music competition where each class was given a copy of a song 'Ditch the Fizz' and were challenged to produce their song/rap with a healthy drinking message. This involved additional time without the investigator present, with some schools including it into their music programme for the term. The final session involved group presentations of a classroom collage depicting what the children had learnt over the year. An interactive classroom quiz based on a popular TV games show was also used. Throughout the year, the children were encouraged to access further information through the CHOPPS link on the hospital Internet site.

After 12 months, the percentage of overweight and obese children increased in the control clusters by 7.5% compared with a decrease in the intervention group of 0.2% (95% CI 2.2–13.1%, P=0.008). Consumption of carbonated drinks decreased in the intervention group compared to the control group (95% CI 0.1–1.3, P=0.03). This specific health education initiative demonstrated that education promoting a reduction in the consumption of carbonated drinks prevented a further increase in the prevalence of childhood overweight and obesity.

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Mechanisms of promoting obesity

Although there are likely to be many factors implicated in the development of obesity, growing evidence suggests a link between the consumption of soft drinks and obesity, especially in children.

Small changes in energy intake and output appear to have a major impact in obesity risk.18 For example, the daily consumption of one can of a regular carbonated drink (120 kcal) over a 10-y period in a constant environment theoretically will have the potential to result in a 50 kg weight gain.19 Reducing daily intake by a small amount of calories or by increasing energy output (the 'energy gap') may help to prevent weight gain. Using data from national surveys, Hill et al19 have suggested that altering the energy gap by 100 kcal each day would prevent excessive weight gain in most adult Americans. For children, the energy gap may have to be more than 200 kcal/day to have a similar preventative effect.20

Another important factor is the glycaemic index (GI) or the rate of absorption of carbohydrate after a meal.21 Low GI diets lower postprandial glucose and insulin responses, whereas high GI diets stimulate lipogenesis and cause increased adipocyte size.22 The GI of the American diet has increased in recent years, and this may be contributing to the rising obesity epidemic.21 The effect of GI on energy metabolism and voluntary food intake has been studied with a small sample of obese boys. On different days, the boys were given meals with varying GI's and their ad libitum food intake for a 5-h period was monitored. It was found that different meals that contained the same amount of energy but had varying GI's had very different effects on metabolism, perceived hunger and additional food intake. The voluntary food intake after the high GI meal was 53% more than after the medium GI meal, and 81% more than after the low GI meal. This suggests that the rapid absorption of glucose after a high GI meal can promote excessive food intake.23 Another theory is that additional calories in liquid form are less satisfying than food solids. Children especially have difficulty in compensating for additional calories, particularly those calories in liquid form. Most individuals compensate for additional calories by consuming less at subsequent meals. Sweetened soft drinks have a high-energy intake but very low satiety value.24

The research by Schulze et al15 also highlighted that the women who consumed the most sugar-containing drinks also tended to smoke more, have a higher calorie intake and do less physical activity. Perhaps the consumption of these drinks could also be marker of a tendency for an unhealthy lifestyle.25

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Conclusions

The World Health Organisation's report on obesity in 1997 concluded that with the trends of increasing adult and childhood overweight and obesity, it was essential to focus not only on individuals with a high BMI and associated health problems. Preventive public health strategies that included populations as a whole are necessary to combat the problem.26 Family-based approaches are best suited where the problem of overweight or obesity has already been recognised,27 and education programmes and schools provide the ideal environment for prevention strategies.28 James et al17 have demonstrated that it is possible to prevent further increases in childhood obesity through a specific health education targeting a reduction in the consumption of carbonated drinks.

Current research suggests that the association between obesity and soft drinks occurs at all ages. The mechanism may not be fully understood, but there is evidence to suggest that preventing consumption of sugar-sweetened drinks has a major role to play in obesity prevention.

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