The Role of Microbiome in Recurrent Obesity Before and After Antibiotic/Placebo Treatment

This is a placebo-controlled, double blinded interventional study evaluating the effect of antibiotic treatment in the prevention of weight regain after a successful weight loss intervention. Volunteers will be recruited in the following ways: e-mail, and social media. Volunteers wishing to participate will be asked to complete a questionnaire regarding the aforementioned inclusion and exclusion criteria. Volunteers who qualify for the study will be invited to an introductory meeting at the Weizmann Institute of Science. The details of the experiment and potential risks or discomforts involved in it will be presented, after which the volunteers will sign an informed consent form. Volunteers will start the study and become active participants for a maximal duration of one year. Samples collected for the study will be used for microbiota profiling (stool and oral), metabolomics (stool, blood) and for bomb calorimeter (stool). The study will comprise of four parts: 1. Baseline - one week of profiling and screening. 2. Nutritional intervention - weight loss intervention which will be based on personalized hypocaloric diet restriction. Meetings will occur twice a month starting from the second week of the study for a three-month period. 3. Antibiotic treatment - 10 days of either antibiotics- Augmentin (amoxicillin+clauvonate), 875mg, 2 /day, or 10 days of placebo pills, 2/day. 4. Follow-up meetings - total follow up of 9 months after antibiotic/placebo treatment. Meetings will occur once a month for the first 3 months of the follow up period, and once every 3 months, afterwards.