Only one way to fight hair loss?

So I've done my basic research. I know the body converts testosterone into dht which then binds to the follicles in your hair, which have a genetic pre-disposition to be more receptive to said binding process.

In essence, your diet, exercise, positive thinking, etc. have no real influence on preventing your hair loss because none of those things stop your body from producing dht or stop your hair follicles from being receptive to dht. A better diet and exercise might improve the texture and strength of your hair but its not going to grow any back or prevent any from falling out in the future. When it comes down to it fin is really the only effective treatment that can.

I am correct in thinking this? Or are there more complex factors in the cause and prevention of hair loss? I'm wondering because I have a pretty crappy diet and I hardly exercise and I'm curious if changing this will have any significant effect on my hair.