Here is the design of a clinical trial:

Official Title: The Emirates Heart Health Project: A Stepped-wedge Cluster Randomized-controlled Trial of a Family-based Health Coach Guided Dietary and Exercise Intervention for Reducing Weight and Cardiovascular Risk in Overweight and Obese Adult Nationals of the United Arab Emirates.

Included conditions:
- Overweight and Obesity
- Cardiovascular Risk Factor

Study Armgroups:
- {'label': 'Family-based intervention', 'type': 'EXPERIMENTAL', 'description': 'These participants will undergo the health coach based intervention with fitness tracker and diet changes, which will be delivered to all family members who meet the inclusion criteria and are enrolled in the study.', 'interventionNames': ['Behavioral: Family-based diet and exercise intervention']}

Interventions:
- {'type': 'BEHAVIORAL', 'name': 'Family-based diet and exercise intervention', 'description': 'The participants will meet together weekly as a family unit to receive education and planning to implement diet and lifestyle changes under the supervision of a health coach. This coach will also be available during the week by telephone or messaging for additional individualized support if needed.', 'armGroupLabels': ['Family-based intervention']}

Primary Outcomes:
- {'measure': 'Weight', 'description': 'Weight (change from enrollment to end of intervention)', 'timeFrame': '16 weeks'}

Please estimate the sample size based on the assumption: 
The study will use an unpaired t-test for comparison. The design aims for a power of 80% and a one-sided significance level of 5%. An interim analysis will be performed after four clusters have completed the intervention to re-calculate the required sample size.
Sample size
          In order to calculate an appropriate sample size without reliable information on the intracluster correlation we will calculate our sample size in terms of the number of clusters required. This also takes into account the cluster design of the study. The sample size in terms of individuals will then be the required number of clusters times the average cluster size.
          For this purpose, we assume that the natural fluctuation in cluster mean weight change (i.e., the standard deviation in mean weight change among clusters) is 3.5%, i.e., half the target weight reduction of 7%. This assumption is based on (or rather inspired by) variation in BMI between successive waves (approximately 5 years apart: much longer than our follow-up period) observed in the Framingham Study [29] where the standard deviation in individual weight differences was between 6% and 7%.
          We will assume that we compare the two groups using an unpaired t-test.
          For a two-armed parallel cluster randomized design to achieve a power of 80% and a one-sided significance level of 5%, we would need four clusters in each trial arm, i.e., a total of eight clusters [32] Since the stepped-wedge cluster design that we have selected is more efficient than a parallel design [33], this sample size should be adequate given our assumption. However, to accommodate for unduly optimistic assumptions about the standard deviation in weight changes we will increase our total sample size to 10 clusters.
          An interim analysis will be performed once four clusters have completed the intervention and the required sample size will be re-calculated on the basis of observed fluctuations in parameters; if this leads to the conclusion that more than 10 clusters are required to detect a statistical significance in the primary outcome, the team will meet to discuss how and if the sample of clusters can be extended.