5'11 146 and you are afraid to lose muscle?? With all due respect, I don't even think you have much muscle at that height/weight
. Eat cleat, do your cardio, and increase your calories above what you need per day. Nutrition is your priority. If you have trouble eating 6 meals a day and staying above your BMR, then look into a weight gainer (a creatine based product). As long as you are eating well and keeping up your cardio and weight lifing (lift BIG! Think low reps high weight), you wont be gaining much bodyfat at all.