Introduction: The influence of tea or coffee supplementation on body weight in adolescents has never been tested. The aim of the present study was to investigate the effect of tea and coffee consumption on body weight and body fat in an obese adolescent population.

Methods: Randomized clinical trial, parallel group study comparing 3 weight loss interventions comprised of a similar dietary recommendation with either coffee (coffee group), tea (tea group) or placebo (herbal tea). Sociodemographic data and medical history details were retrieved from medical files. The body mass index Z (BMI Z) score and fat percentage as measured by bioelectrical impedance were compared between groups at 3 and 6 months.

Patient Population The participants were recruited at the at the Obesity Clinic in the Pediatric Gastroenterology Unit at "Dana Dwek" Children's Hospital from January 2018 and December 2020. The Obesity Clinic is a tertiary referral center for children and adolescent with obesity and its complication. Adolescents aged 12-17 years with BMI in the 95th percentile or higher were eligible for the study. Exclusion criteria included major medical, chronic use of medication that may affect study outcomes or regular intake of some tea or coffee (individual for whom the intervention would likely produce relatively little change in habitual intake).

Study Design This is a randomized clinical trial, parallel-group study comparing 3 weight loss interventions comprising standardized dietary recommendation either with coffee (coffee group) tea (tea group) or placebo (herbal tea). The study consists of 2 weeks run in period and 24 weeks treatment period.

Intervention The 3 groups received similar weight reducing interventions comprising diets that will differentiated only with regard to the recommendation for coffee or green tea consumption. The standard intervention included 2 weekly family-based counseling concerning nutritional education (low carbohydrate, low glycemic index diet), behavioral counseling and physical activity.

The coffee group instructed to consume 2 cups of coffee a day, amount that was previously describe as beneficial in epidemiological studies and safe for children and adolescence. Each cup of coffee contains 250 ml of coffee, which contains approximately 80 mg of caffeine. The children were allowed to add milk to the coffee and sweeten it with artificial sweetener.

The green tea group will be instructed to drink 3 cups (230CC) of Chinese green tea (Wissotzky Tea Israel Ltd). Each tea bag contains 500 g fine dried herb parts. Each cup contains 84 mg total catechin and 32 mg caffeine. The participants were instructed to leave the tea bag for 2 minutes before drinking. The control group consumed 3 cups a day of Wissotzky- kid drink (Wissotzky Tea Israel Ltd), which is a drink that is marketed for children containing infusion of fruits and plants. Each tea bag contains 2.7 gr plants parts with no evidence of polyphenols or caffeine.

The tea was provided to the participants and adherence was ensured by 3 days dietary questioners at each visit and by collecting empty boxes every month.

Outcomes

Information retrieved from medical files of subjects included:

1. Sociodemographic characteristics: age, sex
2. Medical history: perinatal characteristics (birth weight, gestational age), medications and family history of cardio-metabolic diseases (diabetes, hypertension, dyslipidemia, cardiovascular disease, and cerebrovascular episodes) in first- and second-degree relatives.
3. Physical examination: systolic and diastolic BP and anthropometric measurements (height, weight, calculated BMI and body fat)
4. Screening for obesity-related comorbidities: laboratory metabolic workup, abdominal ultrasonography (steatohepatitis) and polysomnography findings (obstructive sleep apnea).

The primary outcomes of the study were decrease in BMI Z score, Percentile and body fat at 3 and 6 months of the intervention.

Weight and height was assessed at baseline and monthly for 3-month period and again after 6 month. Body weight and fat percentage was indirectly measured by BIA (Tanita Body-Composition Analyzer, Tanita DC-360 S and GMON Professional Software), which has been clinically verified to be accurate and reliable and to provide highly reproducible results. The GMON software provides the BIA data adjusted for sex, age, height, and race (Caucasian and Asian) according to reference ranges 12The BMI Z score and percentile was calculated using reference data for sex and age. Metabolic parameters documented upon admission included glucose, insulin, HDL, LDL, TG, ALT AST CRP. Fatty liver and fibrosis was assessed by ultrasonography. At each monthly visit the participant provided 3-day dietary questionnaire.

Definition of Study Variables BMI percentiles and Z-scores of anthropometric measurements were calculated with PediTools Electronic Growth Chart Calculators based upon CDC growth charts. The height, weight, and BMI values were converted to sex- and age-specific z-scores according to the CDC 2000 growth charts. Weight status was defined according to the BMI z-score as follows: overweight as a BMI percentile ≥85th and <95th percentiles (1.036 ≤BMI z-score <1.645), and obese as a BMI percentile ≥95th percentile (BMI z-score ≥1.645).

Childhood MetS components were defined as follows: glucose intolerance = fasting glucose ≥100 mg/dL (5.5 mmol/L); elevated BP = systolic and/or diastolic BP ≥90th percentile for sex, age, and height; hypertriglyceridemia = triglyceride (TG) levels ≥110 mg/dL (1.24 mmol/L), and low high-density lipoprotein-cholesterol (HDL-c) = HDL-c ≤40 mg/dL (1.03 mmol/L).

Obesity-related comorbidities were compiled as follows. Insulin resistance was the calculation of Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) by fasting insulin μU/mL x fasting glucose mmol/L/22.5. The healthy range for HOMA-IR was defined as a value between 0.5-1.4, early insulin resistance was defined as a value ≥1.9, and significant insulin resistance was defined as a value ≥2.9. Nonalcoholic fatty liver disease (NAFLD) was suspected in a child with typical clinical features (obesity and persistent mild elevations of serum alanine aminotransferase [ALT] >2 x upper limit of normal). A provisional diagnosis of NAFLD was made by excluding other causes of liver disease through a focused history, physical examination, laboratory evaluation, and an abdominal ultrasound showing increased echogenicity suggestive of fatty liver. Obstructive sleep apnea was defined by recurrent events of partial or complete upper airway obstruction during sleep as detected by polysomnography performed in patients with a history of persistent snoring and/or recurrent awakenings. Pseudotumor cerebri was diagnosed according to the modified Dandy criteria: symptoms and signs of increased intracranial pressure (e.g., headache, transient visual obscurations, papilledema, visual loss), no other neurologic abnormalities, elevated intracranial pressure with normal cerebrospinal fluid composition, and a neuroimaging study that shows no etiology for intracranial hypertension .

Statistical Analyses SPSS (IBM Corp. Released 2016. IBM SPSS Statistics for Windows, Version 27.0. Armonk, NY: IBM Corp.) was used for all statistical analysis.

All statistical tests were two-sided. The Kolmogorov-Smirnov test and the Shapiro-Wilk test were applied to assess the normality of continuous data. The data are expressed as means±SDs for normally distributed variables and median and interquartile range [IQR] for skewed distribution. Pearson's chi-square test was performed to compare the distribution of categorical variables between 3 intervention group. Kruskal wallis test followed by Dunn's post hoc test was used to compare the differences between Coffee Tea and placebo for continuous variable . The changes over time were compared for each arm separately using Friedman's test for paired data followed by Dunn's post hoc test. A P value ≤0.05 was considered significant.

Inclusion Criteria:

• Adolescents aged 12-17 years with BMI in the 95th percentile or higher were eligible for the study.

Exclusion Criteria:

• Exclusion criteria included major medical, chronic use of medication that may affect study outcomes or regular intake of some tea or coffee (individual for whom the intervention would likely produce relatively little change in habitual intake).

the individual participant data will be anonymous to other researchers