What is the #1 key to maximizing a man's health? Without question it is fighting inflammation. Yes, there are other worthy candidates such as insulin, cortisol and estrogen. But in my opinion, inflammation is the Great Destroyer.
And let me tell you why this subject is so important: if you decrease inflammation, you will be surprised at how much better you feel, look and perform. More importantly, you will attack at the source almost every major source of disease.
Most guys reaching my site are middle-aged and beyond. For us, mortality has suddenly become reality. There can be some fear there, but, as I will show below, inflammation attacks at the root virtually all of the major sources of death and disease. If you get inflammation, you can live a life without fear with maximum energy and productivity.
Don't believe it? Then just look at this short list of nasty conditions that are aided and abetted by inflammation:
1. Heart Disease. One of the root causes of cardiovascular disease is inflammation. In fact, what is interesting is that some experts are arguing that inflammation is THE root of heart disease. For example, studies have shown that 1) hs-CRP (highly sensitive C-Reactive Protein) is the strongest predictor of heart disease and 2) individuals with relatively low LDL ( < 120 mg/dl) but high hs-CRP had a high risk of cardiovascular risk. 
2. Erectile Dysfunction. This is such an important that I covered it in another link on Inflammation and Erections. Suffice it to say, though, that some experts have argued that low-grade inflammation is actually the root cause of most erectile dysfunction.
3. Cancer. TNF-alpha, the infamous inflammatory cytokine, can easily become a cancer-causing machine: if you have enough of this, it singlehandedly will help birth new cancers cells, aid in their survival and promote their spread throughout the body. It also increases a host of other pro-cancer cytokines.  This is why research is beginning to link inflammation to colon , breast/lung  and prostate cancer . NOTE: For additional information, see my link on How to Prevent Cancer.
4. Insulin Resistance. This plague of modern man and core symptom of Metabolic Syndrome has TNF-alpha as one of its primary root causes. 
5. Diabetes (Type II). Not too surprisingly, based on #4, C-Reactive protein is a risk factor the development of diabetes. 
6. Multiple Sclerosis, Crohn's Disease and Rheumatoid Arthritis. TNF-alpha has been associated with all of these nasty autoimmune disorders. 
This list could continue, but the point is that inflammation causes and exacerbates all of the Big Three Killers of modern man: cardiovascular disease, cancer and autoimmune disorders. If you can keep these three in check, obviously your risk of death and debilitating disease will go down dramatically.
Ironically, almost everything we do in a modern, Western lifestyle actually promotes inflammation, as I outline in my link on How to Reduce Inflammation. It would be difficult to live a more pro-inflammatory lifestyle than that experienced by modern man. Almost all of us are trained, from early childhood, in a lifestyle that literally maximizes systemic inflammation and puts us at risk for a potentially miserable life before a premature death, unless we get this monster under control.
2) Biochemical Pharmacology, 2006, 72:1605-1621, "Inflammation and cancer: How hot is the link?"
3) Gastroenterology, 2010 Jun, 138(6):2101-2114, "Inflammation and colon cancer"
4) J Clin Invest, 2007 Dec 3, 117(12):3660 3663, "IL-6 involvement in epithelial cancers"
5) Nature, 2007 Apr 5, 446(7136):690-4, "Nuclear cytokine-activated IKKalpha controls prostate cancer metastasis by repressing Maspin"
6) Journal of Clin Investigation, May 2 2005, 115(5), "Inflammation, stress, and diabetes"
7) Diabetes Care, 2007 Oct, 30(10):2695-9, "Risk of type 2 diabetes attributable to C-reactive protein and other risk factors"
8) Arthritis Rheum, 2001 Sep, 44(9):1977-83., "Demyelinating and neurologic events reported in association with tumor necrosis factor alpha antagonism"