What is the best way to get toner and build muscle as someone who is very slim.

noahcarvalhoamorim9932

I have a very think body. I use to weigh 124lb but now I am 145lb. I have very little fat on my body and would say most of my weight comes from my muscular legs. I want to build my upper body chest,shoulders and back while not gaining fat. How would I do that? Any help would be appreciated.