A double-blind, randomized trial of the efficacy of replacing sugary drinks by low-sugar alternatives on body weight and fat mass in school children.

BACKGROUND Liquid carbohydrates are thought to be less satiating than solid carbohydrates, and calories from sugary drinks might not be compensated for by eating less at subsequent meals. Sugary drinks –including soft drinks as well as fruit juices - are therefore thought to be one of the causes of overweight and obesity in children. However government policies to reduce intake have been less than firm. One reason may be that the evidence for an effect of sugary drinks on body weight rests mostly on observational epidemiological studies and a few short term interventions. The observational studies may suffer from confounding by diet and lifestyle and the trials were too short and too small to be convincing. High-quality randomized controlled trials have a decisive impact on policy and medical practice. Therefore, properly conducted trials are urgently needed to prove definitely that reduction in the intake of sugary drinks reduces body weight in children. Alternatively, if such an effect is not seen in a high-quality trial then other, more effective interventions may be pursued and implemented. AIM Here we propose the first double-blind, long-term, randomized controlled trial of the effect of replacing beverages with sugar by low-sugar alternatives on body weight and fat mass in school children aged 5-10 years. This will be the first trial in this field that meets the demands of evidence-based medicine. DESIGN AND POPULATION Five hundred healthy children (5-10 years) will be divided into 2 groups by lottery. Group 1 (n=250) receives 300 mL per day of sugar-containing drinks for 18 months and group 2 (n=250) receives 300 mL per day of a specially developed, identical-looking, sugar-free version of the same drink. Only children who already habitually consume 300 mL per day or more of sugary drinks are eligible. They will replace their habitual drinks with the study drinks, without a need to change their drinking habits. The lottery ensures that diet and activity will on average be the same in both groups. The drinks will be consumed during the morning break at school and consumption will be supervised by the teacher in order to check whether the children actually drink the study drinks. The empty packages will be collected and counted in order to check compliance. No instructions will be given on food selection or intake so as not to disturb spontaneous adjustments in intake brought on by the study drinks. STUDY OUTCOMES The primary outcomes of the study are the children’s body weight and body fat mass as estimated from waist circumference (cm) and skinfold thickness (mm) at 4 sites. This will be measured in all children at the start and the end of the study and differences between changes in the two groups will be evaluated. As a secondary outcome we will also assess food intake of the children at lunch time - shortly after the morning break when the children have consumed the study drinks - in order to check whether intake of energy differs between the groups. This may indicate whether or not calories from the study drinks are or are not compensated for by changes in food intake. IMPLICATIONS If this trial shows that intake of sugary drinks promotes weight gain, public health strategies and policies to discourage consumption of sugary drinks should be (more strongly) pursued and implemented. This will be an incentive for industries to lower the amount of sugars in beverages and to develop special sugar-free beverages for children.