in part, because I've witnessed my dad's health markedly deterioriate over the past few years (he was recently diagonsed with prostate cancer and he also has some sort of autoimmune disease that is causing him to have a very low blood platlet count).

In my dad's case, I think three things really set him back.

The first is that he broke his leg about a decade ago and never fully healed from it, which, over time, has really affected his mobility and flexibility (this, in combination with low energy from the autoimmune disease, has resulted in him being very sedentary).

The second is that his diet for a long time has been pretty poor. My dad has always loved sweets and sugar. In an effort to keep his weight down, he started skipping meals. But this resulted in him snacking on a lot of sugary treats in lieu of eating a meal. He also tends to drink a lot of calories in the form of sugary beverages (he loves chocolate milk, fruit smoothies, and milkshakes). Conversely, he hates (and tends to avoid) most vegetables. Along those lines, I'd guess that somewhere near half his caloric intake over the past 5 or so years has been from some form of sugar. Meanwhile, I believe he's been starving his body of nutrients.

The third is more of an emotional issue. In that regard, I believe people tend to fall on a spectrum between being "external" (where their sense of meaning and fulfillment comes from interactions with others) and "internal" (where their sense of meaning and fulfillment comes from within). My dad tends to fall more on the external side of the spectrum and since he retired about 5 years ago, he's struggled with depression and boredom.

Anyway, my dad's situation has been a motivator for me to research factors that affect longevity. In that regard, it's been interesting to read about contemporary research that study how factors like hormones (e.g., insulin, testosterone, cortisol, etc.) and hormone response as well as gut, liver, and immune system health may affect overall health, body composition, and longevity. It's also been interesting to study how such factors may be influenced by lifestyle choices, particularly diet, exercise, sleep, and stress.

While many of these studies are still in a very theoretical stage, it seems like we're starting to learn many things that were not considered by our parents' generation (in much the same way previous generations, for example, underestimated the dangers of smoking, etc.).