Losing muscle mass, putting it back on?

I'm on day 9 of my first 10 day MC. I was about 8-10 lbs overweight when I started and I've lost 1 lb. per day; so 9 lbs up to today. I'm NOT doing this to lose weight (want to start eating more organics/less meat) however I would like to put back on healthy pounds next week. I exercise regularly, I had gained the weight in the last 6 months due to a knee injury/surgery.
I've been exercising while on the MC, hiking 3-4 miles, running 2-3, weight training, etc. Yesterday (day 8) I was pretty weak during my workout. I've lost some muscle and my question is, how do I put muscle back on when I'm done with the MC? Proteins obviously, but I'm not sure when to start incorporating them back into my diet next week. I'm also going to start Pilates again.