Here is the design of a clinical trial:

Official Title: The Impact of a Powdered Meal Replacement on Metabolism and Gut Microbiota: a 12-week Study in Individuals With Excessive Body Weight

Included conditions:
- Dietary Modification

Study Armgroups:
- {'label': 'Control Group', 'type': 'NO_INTERVENTION', 'description': "Those assigned to the Control group will be asked to maintain their usual dietary intake over 12 weeks. Participants' usual dietary intake is expected to reflect the North American dietary pattern (i.e. \\~15% of total energy intake coming from protein, \\~50% from carbohydrate and \\~35% from fat)."}
- {'label': 'Powdered Meal Replacement Group', 'type': 'EXPERIMENTAL', 'description': 'Those assigned to the Powdered Meal Replacement group will be asked to maintain their usual dietary intake and consume a powdered meal replacement composed of soy protein, honey and yogurt twice daily (in two snacks) over 12 weeks. The addition of the nutritional supplement to a North American Dietary Pattern (described on the CON group diet) will result in a diet composed of, approximately, 22% of protein, 48% of carbohydrate and 30% of fat of total energy intake. The amount of protein is considered higher than the North American dietary pattern (i.e. 15%); however, still within the Acceptable Macronutrient Distribution Range (AMDR) recommended by the Dietary Guidelines for Americans (10-35%).', 'interventionNames': ['Dietary Supplement: Soy protein, honey and yogurt.']}

Interventions:
- {'type': 'DIETARY_SUPPLEMENT', 'name': 'Soy protein, honey and yogurt.', 'description': 'Participants will be asked to maintain their usual dietary intake and consume a powdered meal replacement composed of soy protein, honey and yogurt twice daily (in two snacks) over 12 weeks. The addition of the nutritional supplement to a North American Dietary Pattern (described on the CON group diet) will result in a diet composed of, approximately, 22% of protein, 48% of carbohydrate and 30% of fat of total energy intake. The amount of protein is considered higher than the North American dietary pattern (i.e. 15%); however, still within the Acceptable Macronutrient Distribution Range (AMDR) recommended by the Dietary Guidelines for Americans (10-35%).', 'armGroupLabels': ['Powdered Meal Replacement Group']}

Primary Outcomes:
- {'measure': 'Interleukin-6.', 'description': 'Changes in blood interleukin-6 will be assessed at baseline, middle and end of the 12-week dietary intervention period.', 'timeFrame': 'At baseline (week 1), middle (week 6) and end (week 12) of the intervention period (12 weeks).'}

Please estimate the sample size based on the assumption: 
Significance level of 5%, power of 80%, and a 20% attrition rate.
Sample size estimate
          A total of 74 participants (37 in each group) will be needed to detect a medium effect size (ES) of 0.669. The ES was calculated based on a previously published study,30 in which the mean per cent change in IL-6 from baseline to 12âmonths was â6.76Â±36.95âpg/mL in a group receiving soy protein versus 17.62Â±35.92âpg/mL in the CON. Accounting for a 20% attrition rate, the total sample size of 88 participants (44 in each group) will have a power of 80% with a significance level of 5%. The sample size calculation was done using G*Power V.3.1.9.2.