I've read so many studies that show how diet and exercise and vitamin supplementation can boost your natural T levels (still within the natural range, though). And sleep of course. I encourage you to search around the web.

What's kind of scary is that the natural range is so large - like 300 - 1000 ng/dl for testosterone, but you will literally feel like a different person if you fix all of the above factors properly and go from say 350 to 600. And living in that higher T state for months and years at a time, you will start to look different as well (generally in a good way for men).