I am a 43year old male with a history of diabetes. I have kept my diabetes in check by a combination of strength training and cardio. I recently tore my rotator cuff and had it repaired. During my recovery and rehab, I will not be doing any major lifts that will burn significant calories or induce muscle growth. I am able to do cardio. Question: what diet will preserve the most muscle mass while allowing me to lose fat while I am in the cardio only phase of rehab? I am about a week after surgery and my pants are getting tight. I need to diall it back a bit and am considering a keto/ Atkins approach, but don't want to lose too much muscle. I am thinking that just a balanced diet with a little extra protien and a little less carbs, with cals set jus below maintenance might be better than drastically cutting carbs and going with an Atkins based approach.

Goal is to slim down a bit until i can start bangig the weights again.