Interesting meta-analysis I came across today showed that men that increase their testosterone levels not only helps them improve their sperm production, but also helps them lose weight, increase insulin sensitivity (to reduce diabetes risk), and reduce total cholesterol and triglycerides (lowering risk of cardiovascular disease and mortality).
So dive in, do your research, figure out what you can do to increase your testosterone, and things you should stop doing that may be reducing your testosterone.
Reference – https://www.ncbi.nlm.nih.gov/pubmed/26537862?dopt=Abstract