Hello, Katherine, Thank you for asking question. I am Dr Adil, I would have liked to know why you had sigmoid colon resection, what was the reason...! anyhow, First of all, sigmoid colon connects descending colon with the rectum. Sigmoid colon also contains fecal material that is ready to leave the body. Rectum has the ability to store it. So sigmoid colon absence doesn t cause a major disability, except, mild fecal urgency or mild diarrhea, although not very serious. Colon absorbs 90% of water and electrolytes, Major percentage of nutrients are absorbed in small intestine, you still have all the small intestine and major portion of colon. So Sigmoid resection, i don t think can affect you much (again, i would like to know the reason of sigmoid resection in order to have a better idea of your condition). I must say, your weight gain is related to poor unbalanced diet, lack of exercise or both. If you have more questions i would be glad to answer them. Kind Regards. Dr Adil Ramzan