Is getting tattoos haram?

I did my research on the subject; there is a lot of controversy (it is in hadith but not in the Quran), and generally, it is classified as an alteration of God's creation. But I personally don't believe it to be, because if that were the case, then eating unhealthily and not sleeping enough...are also haram, as they alter the way your body looks and harm you. In my opinion, tattoos hurt nobody and are just a beautification of the body. So please, when answering my question, leave culture out and comment on the religious factor only.