Have you heard that apple cider vinegar will help you lose weight? The only study to test the idea in people was done in Japan. In the study, 175 obese but healthy people took either vinegar or water daily for 12 weeks. Their diets were similar. They kept food journals. At the end of the study, those who used vinegar had lost slightly more weight. On average, the vinegar group lost 1-2 pounds over the 3-month period. They gained it all back after the study was over.