I hope you have started back on your pred by now. It is not vain of you to worry about
your weight. This is a very real reality for ALL of us. Also, don't feel like you need to starve yourself, either. This just will not work. You will feel awful!
Have you considered seeing a nutritionist? This might be helpful for you to get you on a plan that meets your dietary needs but, also, help you trim calories. Last summer I did this and it was very helpful - I only saw her two times but it was very helpful.
Also, could you invest in a few sessions with a personal trainer? A trainer can help you with exercises that won't hurt your joints. The best thing for us, according to my trainer, is to walk. Walking is a great way to burn calories and tone muscles and it is inexpensive. I only have time for consulting these "experts" in the summer. I just use what I have learned now. It was very helpful.
I did not actually lose much weight from this because I flare enough to need to slow down on my exercises. My diet changes have been wonderful though. I feel better when I stick to my new rules for eating. If I get lazy or cheat, I can really tell. I have been successful in keeping 5-10 ounds off, however, and I plan to continue and keep losing weight slowly. (I did just increase my pred, though, so - who knows?)
I'll keep you in my prayers!
Lupus and RA and LOTS of Medications!