What Jeff said, you want to focus on getting healthy so you can get off the pred. I (like Ben Morrison) gained about 8 pounds of face on pred, but I didn't gain anything other than cheek (seriously) only because by default I'm used to watching what I eat and controlling it.
If you're on pred, especially a high dose like that, you probably shouldn't workout much, my GI instructed me no weight training at all the whole time I was on it until about 10 mg a day....It puts too much stress on the heart and hormones as it is. Every appointment, I'd ask him if I could go workout again, and get his head shaking. The sooner you can get off pred, the sooner you'll be better (usually how it works unless pred's not doing enough for you, like it did with me), and then that means the sooner you can work out. Now I'm not up to it much and it's quite difficult due to symptoms, but if your doc says it's okay, and your symptoms allow it, go for it.
For now, I'd say talk to your doctor on it, ask what he thinks about your state of health and disease to find out what activities you can do. If you haven't been doing well lately, a few extra calories and some moderate activity (if able) may help you bounce closer to your normal weight, it just may help you gain a few extra muscle-pounds, if you used to have it. The body is odd like that, if you've lost muscle recently, it's possible you may gain some back just by doing some normal activities, kind of like when someone gets Mono or a bad illness for a few weeks, is bed ridden, and they lose muscle (and water & fat), then gain some muscle back when they resume normal activities again, even without weight training. The body has normal amounts of muscle for normal tasks (walking, going up stairs, lifting "normal" objects, carrying "normal" things, etc...) and if you've lost that, as it sounds like (from your first post saying you dropped a bit), you may be capable of gaining it back fairly easily.
Don't pig out, your first inclination in your post was right, not just for blood cholesterol levels, but for just about every other logical reason not to.
Rather than tell you to come back when you're capable or wanting to lift weights, these are some of the threads Jeff mentioned...
http://www.crohnsforum.com/showthread.php?t=3482
http://www.crohnsforum.com/showthread.php?t=3343
http://www.crohnsforum.com/showthread.php?t=3528