Men are put off of sex because they feel insecure and because they worry about losing their freedom within a relationship. The University of Kentucky study found that unlike women, men often lose interest in sex when they are unhappy or insecure.

Why do guys lose interest after sleeping with a girl?

When a man is having sex his testosterone goes up. Immediately after orgasm, his T (testosterone) levels go back to normal. And when a mans testosterone levels decrease, he feels less like a man. He feels the need to pull away and may even lose interest for a while.