You need plenty of protein and healthy fats in addition to carbs. Fish, flax and olive oils are excellent for healthy fats. Avacado and nut butters. Nut butters would be easier to digest than eating nuts. Eggs, lean white meat of turkey and chicken and whey protein isolate or egg white protein are good sources for easy-to-digest proteins.
I'd highly recommend you supplement your diet with Absorb Plus shakes. These are formulated specifically for IBDers and are basically predigested, so even an impaired digestion can get the nutrients it needs. The formula is much healthier than most OTC weight gain/meal replacement supplements - like Boost and Ensure - which often have high amounts of sugar and unhealthy fats.
L-glutamine, Mucosaheal and George's aloe will help with gut healing so you'll be able to better digest and absorb what you're eating. That's part of the equation. You can stuff yourself all you want, but if your digestion is severely impaired, you won't be able to properly break down your food and access the nutrients.
I'd also recommend you start a gentle weight training program, if you haven't already. Increasing muscle mass is how you put on healthy weight as opposed to alot of fat. It's also good to rebuild any bone loss from Pred.
Diagnosed with ulcerative colitis spring 1999
Therapeutic dose sulfasalazine.
Probiotics, l-glutamine and fish oil caps. George's aloe vera juice and Mucosaheal.