BMJ  2006;332 (22 April), doi:10.1136/bmj.332.7547.0-e

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Reduced consumption of sugary drinks helps the heaviest teenagers to lose weight

Research question Can sugary drinks lead to adolescent obesity?

Answer (possibly) When the heaviest teenagers stop drinking sugary drinks for six months, their body mass index decreases

Why did the authors do the study? Observational studies suggest that sweet sugary drinks such as colas are at least partly responsible for the epidemic of adolescent obesity in the United States. Commentators from the drinks industry argue that the evidence is circumstantial, however, and not robust enough for them to change their aggressive marketing tactics. These authors wanted to test the link between sugary drinks and obesity in a formal randomised trial, the most powerful form of evidence available, by finding out if reducing intake of sugary drinks resulted in weight loss for American teenagers.

What did they do? 103 teenagers (aged 13 to 18) from one US high school took part in a preliminary pilot trial to assess whether replacing sweetened drinks with calorie-free alternatives would have any effect on their body mass index. The authors randomised participants either to receive their choice of calorie-free drinks (such as diet drinks and bottled water), delivered directly to their home, or to continue with their usual drinking habits. Participants assigned to the intervention also had monthly telephone counselling about avoiding sugary drinks.

The authors estimated participants' energy intake from sugary drinks at baseline and again at the end of the trial, using structured telephone interviews. The trial lasted 25 weeks.

What did they find? Teenagers assigned to the intervention reduced their intake of sugary drinks by 82%. There was no change in the control group. In the intervention group, the greatest impact was on the teenagers who had been in the top third of body mass index (BMI 25.6) at the start of the trial—these participants reduced their body mass index by a mean of 0.75 (SE 0.34) compared with the controls (P = 0.03). This effect was independent of age, sex, and baseline consumption of sugary drinks. The intervention had no significant effect on the teenagers in the bottom two thirds of body mass index.

The findings were unaffected by sex, race or ethnicity, age, household income, household size, physical activity, or television viewing.

What does it mean? Although this is only a pilot study, it does show that teenagers' drinking habits can be changed by providing them with healthier options at home and teaching them how to avoid sugary drinks when they are out. It also suggests that if these changes in drinking habits are maintained over six months they can have a detectable effect on body mass index, at least among the heaviest teenagers.

These findings lend support to US guidelines recommending that children limit their consumption of sugary drinks and to the idea that these soft drinks contribute to obesity.

The intervention tested in this study was intensive and expensive, but the authors say it could be modified relatively easily into something more pragmatic and affordable that could and should be evaluated in large scale trials.

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Ebbeling CB et al. Pediatrics 2006;117: 673-80[Abstract/Free Full Text]. Effects of decreasing sugar-sweetened beverage consumption on body weight in adolescents: a randomised, controlled pilot study

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Ditch the Fizz !

David Kerr, et al.
bmj.com, 10 May 2006 [Full text]