Weight loss is common and is usually caused by a combination of factors: loss of appetite, inability to properly digest and absorb what is eaten, increased gut motility (diarrhea) moves contents through so fast, absorption is inhibited. Reducing bleeding and inflammation through a combination of meds and natural supplements will help heal the digestive tract and allow for better nutrient absorption. You may also want to consider enteral nutrition, predigested shakes designed specifically for IBDers. Check out Absorb Plus:
http://www.holistichealthshoppe.com/#6Most gastos don't talk to you about
vitamin supplementation to combat nutritional deficiencies; neither do they usually mention any kind of natural healing approaches like omega-3 supplementation to reduce inflammation. You have to get out there and do your own research on dietary and alternative healing methods. There are alot of great books available. A few I'd recommend are Optimal Digestion, The New Eating Right for a Bad Gut, Listen to Your Gut, The IBD Remission Diet and Breaking the Vicious Cycle.