I never heard such a thing. You can rebuild. Body builders bulk up all the time. It is nearly impossible to add muscle unless you are eating more than you burn and working out. I am planning to go 5 below goal and then try to build muscle getting back to goal. My psyche could not handle taking a break from the diet and doing it now; I refuse to gain back anything I have lost until I am below goal. That's why I am frustrated with my apparent stall of the last several days. I have to start exercising. I will include some barbell work to try to keep from losing additional muscle. I need to bundle up and wear my reflective gear and walk even if it is cold and dark or I need to some up with something I can and will do inside.