Well, holding an atheist paradigm isn't a good starting point as you exclude from yourself the spiritual/psychological options that are available to you.
If you've swallowed the brainwashing, hook, line and sinker, that you are physically, permanently structured to be attracted to the same sex forever, it's certainly not an easy enlightenment that this is not true.
And if you can't possibly embrace the concept that homosexuality is a spiritual/mental condition, and not a physical one, you likely have no chance of changing.
Many who come to the realization that their status of same-sex attraction is a spiritual one, and goes against everything that God intended for mankind, are satisfied to become celibate and deny an unnatural state of being rather than live a life that is an affront to God. God expects everyone to fight against their tendencies all their lives. That is the Cross we each have to bear. For some, it is addiction, for some it is anger, for some it is sexual. It is all sin against God and those who are willing to be held accountable to God will take their stand.
I don't know what the percentage would be of those who make a full change from one sexual proclivity to the other, but for many, it is discovered that sex is not the imperative that they were lead to believe it is and they are very happy to do without.
Besides that, there are documented cases of sexual attractions altered by psychology and the military as well has discovered that it can even be changed on the battlefield. Research it a bit.