Here is the design of a clinical trial:

Official Title: Effects of an Iso-energetic Low Glycemic Index (GI) Diet on Liver Fat Accumulation and Gut Microbiota Composition in Patients With Non- Alcoholic Fatty Liver Disease (NAFLD)

Included conditions:
- Fatty Liver
- Nutritional and Metabolic Disease

Study Armgroups:
- {'label': 'LGI Diet', 'type': 'EXPERIMENTAL', 'description': 'low glycemic index diet', 'interventionNames': ['Other: low glycemic index diet']}
- {'label': 'HGI Diet', 'type': 'OTHER', 'description': 'High glycemic index diet', 'interventionNames': ['Other: High glycemic index diet']}

Interventions:
- {'type': 'OTHER', 'name': 'low glycemic index diet', 'description': '• Three-day cycle menu of LGI diet will be designed and supplied to each participant in an amount designed to meet their estimated energy requirements. The percentage energy from protein, fat and carbohydrate will be the same in the two diets. Each diet period of the trial will last for two weeks.', 'armGroupLabels': ['LGI Diet'], 'otherNames': ['LGI']}
- {'type': 'OTHER', 'name': 'High glycemic index diet', 'description': 'Three-day cycle menu of HGI diet will be designed and supplied to each participant in an amount designed to meet their estimated energy requirements. The percentage energy from protein, fat and carbohydrate will be the same in the two diets. Each diet period of the trial will last for two weeks.', 'armGroupLabels': ['HGI Diet'], 'otherNames': ['HGI']}

Primary Outcomes:
- {'measure': 'liver fat content', 'description': 'To assess the difference in liver fat content between LGI and HGI diet groups in participants with NAFLD using MRI/S', 'timeFrame': 'At baseline'}
- {'measure': 'liver fat content', 'description': 'To assess the difference in liver fat content between LGI and HGI diet groups in participants with NAFLD using MRI/S', 'timeFrame': '2 weeks'}

Please estimate the sample size based on the assumption: 
Two-group t-test (cross-over ANOVA) with a 0.05 two-sided significance level, 80% power, and a dropout rate of 33-40%.
Sample size calculation and justification
        The sample size is calculated using nQuery based on previous completed study by Bawden et al.21 Based on their pilot data, baseline liver fat fractions of both diet groups were 2.4Â±1%â1.2%, and after 1âweek were HGI (High GI)=4.7% Â± 2%âand LGI=1.6 Â± 0.7%. Using a two-group t-test (cross-over analysis of variance (ANOVA)) between the post-diet values with a 0.05 two-sided significance level, this produces a sample size of n=8 in each diet sequence (a total sample size of 16). This sample size has an 80% power to detect a difference in means of 3.1 (the difference between a Treatment 1, Âµ1, of 4.7 and a Treatment 2, Âµ2, of 1.6) with the assumption that the crossover ANOVA sqrt (MSE) is 2.828 (the SD of differences, Ï, is 4). Assuming that 40% of people would drop out from cross-over study design, it is expected that at least 24 participants would need to be recruited.
        The effect from the pilot study by Bawden et al pilot study (n=7) was an average 1.6%Â±0.7% decrease in liver fat fraction after following a 1-week LGI diet (p<0.05). Given that baseline liver fat fraction was 2.4%, in order to see such change with 80% power (p<0.05) we have doubled the participant numbers to n=16 using nQuery software to detect statistically significant differences.21 Our group has recently completed a study (ClinicalTrials.gov Identifier: NCT03844165) in which 84 participants with NAFLD followed either an LGI food enriched diet or their normal diet. Patients who changed their diet were found to have a significant decrease in liver fat after 16 weeks (from 20.4% to 18.8%) and had a statistically significant decrease in fasting glucose levels after the diet compared with the control group patients following their normal diet. This provides strong support to our hypothesis and demonstrates that a simple dietary change can have measurable impact on NAFLD symptoms in a short period. In another previous randomised crossover trial, metabolic changes were seen within 2âweeks in a dietary intervention with 10 participants.66 Based on these different approaches, we conclude that a sample size of 16 at the end of the study is sufficient. Assuming a 33% drop-out rate we estimate that it will be necessary to enrol n=24 NAFLD participants to achieve n=16 completing the two diet-interventions. This dropout rate has been reported in other dietary interventional studies.67