No, entyvio isn't making you gain weight, not a known side effect. We can all gain weight when we heal, are healthier, and regain a good appetite. Might be a nice indirect affect of our meds, to be able to regain some weight. Certainly evaluate your food input calories against output. I know after a year of flaring, I ate like crazy and lots of bad stuff as I could get away with it. In a remission, I had to eat more carefully and could no longer throw all caution to the wind
The only medication within our UC medication cabinet that causes weight-gain is prednisone and other similar steroids.