You are gaining weight because you are finally healthy. I wouldn't worry about it just yet. Take time to fully recover before embarking on a diet. Yes, even though food races through you it does not mean calories are not being absorbed. Calorie absorption takes place in the terminal ileum. Eventually you will be able to take the weight off and it will be just as challenging as with a colon. No secrets, it's all about decreasing calories and increasing exercise.
dx proctitis in 1987
dx UC in 1991, was stable until 1998
1998 started prednisone, asacol, pentasa, nortriptylene, ativan, 6MP, rowasa enemas and suppositories, hydrocortisone enemas, tried the SCD diet, being a vegetarian, omega 3s, flax, pranic healing, yoga, acupuncture, probiotics
2000 lost all my B-12 stores and became anemic
2001 opted for j-pouch surgery- now living life med-free