I had Roux En Y surgery for bile reflux, not for weight loss. My surgeon says that although not likely, antibiotics can cause damage to the stomach in regard to wiping out all the bacteria, which in turn can get into the mitochondria. I have sore hip tendons now whereas I never had this in all my time of doing intense running/biking. But it is the energy that is the main issue with me, just can't generate what I was able to prior to taking this medication. A functional doctor I am seeing as well seems to be convinced this is the root of my problem now, but fixing the gut with a balanced level of bacterial/flora will start the process of healing. Could be some time though. Just not used to being this lethargic all the time, which can be depressing.