I wish I'd known that when I was younger. My hair always been very fine, with no body whatsoever. It's why I've kept it short the majority of my life. I'm 77, and due to thyroid medications, my hair continually falls out, and has thinned even more as I've aged.
I think part of it is the exfoliation that the scalp receives when it’s shaved and while the hair is coming back in. A lot of hair thinning seems to be due to accumulation of dead skin cells that may clog follicles. I’ve tried baking soda, but the aspirin exfoliation looks interesting:
https://www.healthline.com/health/beauty-skin-care/exfoliation-for-scalp
Hasn’t worked for me
I went bald in six months aged 63
Typical 100 hairs on top and thick on sides
Face is covered in grey hair from below eyes to bottom neck including mouth corners
Helluva beard