The Role of Microbiome in Recurrent Obesity

This is a placebo-controlled, double blinded interventional study evaluating high intensity oral fecal microbiota transplantation from lean healthy donors to prevent 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 informed consent forms. Volunteers will start the study and become active participants for a maximal duration of two years, depending on the weight loss process. 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 Mediterranean hypocaloric diet restriction. Meetings will occur twice a month starting from the second week of the study for a three-month period. 3. FMT/ Placebo intervention - 5 weekly cycles of high intensity lean donor FMT/placebo will be administered starting after reaching a weight loss of 5 to 10% of total body weight. Each cycle will consist of 10 capsules administered on two consecutive days (total 100 capsules) 4. Follow-up meetings - total follow up of one year after FMT cycles. Meetings will occur every month for the first 3 months of the study, and every 3 months, Afterwards.