Here is the design of a clinical trial:

Official Title: Effects of Milk Protein Intake in Young Children on Early Growth and Later Obesity Risk: a Multicentre Randomized Clinical Trial

Included conditions:
- Healthy

Study Armgroups:
- {'label': 'Experimental formula', 'type': 'EXPERIMENTAL', 'description': 'Young-child formula with low protein content', 'interventionNames': ['Dietary Supplement: Young-child formula with low protein content']}
- {'label': 'Control formula', 'type': 'ACTIVE_COMPARATOR', 'description': "Young-child formula with protein content similar to that of cow's milk", 'interventionNames': ["Dietary Supplement: Young-child formula with protein content similar to that of cow's milk"]}

Interventions:
- {'type': 'DIETARY_SUPPLEMENT', 'name': 'Young-child formula with low protein content', 'description': 'Young-child formula with low protein content', 'armGroupLabels': ['Experimental formula']}
- {'type': 'DIETARY_SUPPLEMENT', 'name': "Young-child formula with protein content similar to that of cow's milk", 'description': "Young-child formula with protein content similar to that of cow's milk", 'armGroupLabels': ['Control formula']}

Primary Outcomes:
- {'measure': 'BMI-for-age z-score', 'description': 'WHO-growth standard', 'timeFrame': 'Age 24 months'}

Please estimate the sample size based on the assumption: 
A power of 80%, a significance level of 5% (two-sided alpha of 0.05), and an assumed loss to follow-up of 30%.
Sample size
        The sample size calculation is based on the observations from the CHOP-study.1 This trial examined the difference in BMI-for-age z-scores between two groups of children fed a higher or lower protein content formula during the first year of life. At 24 months of age the BMI for age z-score difference between both formula groups was 0.2 SD. The absolute difference in protein content between intervention and control group in the CHOP-trial was lower (Infant formula: 0.8âg/100âmL; Follow-on formula: 1.6âg/100âmL) compared with the ToMI-trial (2.2âg/100âmL). Despite a higher protein difference, we expect a lower effect of the intervention due to the lower contribution of milk to the total protein intake in the second year of life. Thus, we assume a slightly lower mean difference in BMI for age z-score of 0.15 SD at 24 months of life.
        The sample size was calculated with an anticipated effect size on BMI for age z-score of 0.15 SD and a SD of 0.9. Assuming a power of 80% and a significance level of 5% (two-sided alpha of 0.05), a sample size of 566 subjects per intervention arm is calculated. Therefore, 1132 subjects in total are needed. To have enough power to detect also a difference of the same magnitude at 72 months (6 years) of age, at an assumed loss to follow-up of 30%, a final sample size of 1618 subjects was estimated.