hi, I would like to say to you that people tend to loose weight as they age this is partly because as people age the amount of hormones that build up your body like growth hormone ,testosterone tend to decline as you age.Other notable features are due to decrease in appetite due to various other factors like inability to chew food properly and swallowing,some minor infections that get unnoticed ,malignancy ,tuberculosis to say a few.I would definitely recommend you to consult a physician who can evaluate your condition since you are loosing weight inspite of normal appetite.Hope my answer to your question was adequate.