Interesting. I didn't know there was a connection between antibiotics and weight gain. Is it because of their affects on the good bacteria in the gut?Kathryn- when I was in my teens, I was very active, ate an extremely low fat diet, was a vegetarian, and I put on 10 pounds per year. They insisted on giving me antibiotics every time I went to the dentist, twice a year. The consequence was I became obese.