I have a story that relates to this. About 8 years ago, a fitness center opened and I started going. I had lifted off and on since I was 16, but due to where I live, there was no gym. One day one opened in a neighboring town.
Long story short, I started going, and after a few months convinced a married friend to start going. We car pooled for 3 months, and I could see changes in his body and told him so.
I told him, keep this up, and your wife will be all over you. She is going to see changes, and other women are going to notice and tell her.
That is exactly what happened- suddenly she was all over him, couldn't get enough of him.
The reasons are twofold:
a) he looked more attractive, and his improving himself was attractive....
b) Probably most importantly, she realized other women would see this as well, maybe she even heard it from other women, and her competition anxiety rose.
He told me later "You were right, xxxx is all over me."
Alas he decided to "take the summer off" and never went back.
The work and self-improvement can never end gentlemen