Obesity results from an imbalance between energy intake and energy expenditure. There is much speculation about foods that are particularly fattening, and sugary drinks are seen as major culprits. It is hypothesized that a high intake of calories from sugary drinks would not be compensated for by reduced food intake at subsequent meals. As a result, body weight would increase. In this double-blind, long term, randomized controlled trial the effect of replacing sugar-containing beverages by low-sugar alternatives on body weight and fat mass in children will be investigated.

Rationale: Liquid carbohydrates (including soft drinks as well as fruit juices) are thought to be less satiating then solid carbohydrates (e.g., bread or fruits). The hypothesis is that calories from sugary drinks might not be compensated for by eating less at subsequent meals and body weight would increase. In this way liquid carbohydrates might be one of the causes of becoming overweight and obesity. However, the evidence for a causal relation between sugary drinks and weight gain is inconclusive.

Objective: To test the effect of replacing sugar-containing beverages by beverages low in sugar on body weight and fat mass in children aged 5-10 years.

Study design: A double-blind, long term, randomized controlled trial.

Study population: Healthy school children in the age of 5-10 years old. We consider it unethical to encourage children to drink sugary drinks. Therefore children are only eligible if they already habitually consume 250 mL per day or more of sugary drinks.

Intervention: Six hundred healthy children (5-10 years) will be divided randomly into 2 groups. Group 1 (n=300) receives 250 mL per day of sugar-containing lemonade. Group 2 (n=300) receives 250 mL per day of lemonade low in sugar. The low-sugar drinks are sweetened with artificial sweeteners. The drinks will be consumed during the morning break during the weekdays at school and at home during weekends and holidays. The intervention period will be 18 months.

Before the main trial starts feasibility and logistics will be tested in a pilot study. The design of the pilot study will be a 2-month randomized controlled trial in approximately 80 school children aged 5-10 years.

Main study parameters/endpoints: The primary outcome of the study is children's body weight (body mass index, corrected for age). Secondary endpoints are waist circumference, skin folds and bioelectrical impedance. These outcomes will be measured four times during the study, at 0, 6, 12 and 18 months. As a secondary outcome we will also perform a sensory evaluation at 0, 6, 12 and 18 months and a questionnaire about dental health at 12 and 18 months.

Inclusion Criteria:

• Healthy school boys and girls
• Age 5 years and older, children still have to be in elementary school at the end of the study
• Children who already habitually consume 250 mL per day or more of sugary drinks

Exclusion Criteria:

• Using medication or under medical treatment for obesity
• Any acute or chronic disease such as diabetes, growth disorders, celiac disease, or serious gastroenterological diseases
• Medical history or surgical events known to interfere with the study
• Participation in another intervention trial up to 3 months before and during the study, if the intervention interferes with the current study
• Physical disabilities that hamper the measurements
• Intention to change location of residence and primary school during the study period