I injured my back during a workout a couple of days ago. Now I am unable to do any weightlifting or cardio until I recover. I was going great with my workouts and diet, and lost 5 lbs since mid January. The question I have is: How can I keep from gaining it back while I'm laid up? Do I still shoot for 40/40/20 on the macronutrients? Still 1500 calories? Or will the extra protein just be stored as fat if I'm not working out? Will 1500 calories throw my body into starvation mode if I'm not exercising? How do I eat and maintain until I can get back to it?
I apologize if this question is answered elsewhere. I looked but couldn't find anything that suited my situation.

Height?
Weight?
BF%?
Goals?

height: 5'6"
weight: 180 lbs
BF%: Not sure
Goals: Finish PA school, learn to play the guitar, learn to ski, lose 45 pounds and shrink my fat ass.