You are vague on several fronts-- what your illness is, what is the nature of your workouts, and why your illness makes you want to keep to 1 meal a day. My initial thought is that your physical concerns on muscle loss are not an issue with your time of day feeding, as long as your body is telling you that you are eating enough. I think I'd be more concerned about your illness being the root cause of any muscle loss.
The Buck stops here. I am responsible for my past and my future. So for today: I choose to be happy. I will seek wisdom. I will be a servant to others. I will greet this day with a forgiving spirit.