Why is all the muscles in all my arm and all my leg wasting away. I lift weight and it doesn't do anything. I use to be very tone but in losing weigh?

I'm concerned... Unexplained loss of muscle mass in a young person is concerning (especially if it is only on one side of the body) and should be investigated in person with a physical exam and possible labs and other studies (such as nerve studies). Many things can lead to this, including nutritional problems, lack of growth hormone or testosterone, nerve damage, etc. Be sure to be seen by your doctor ASAP.