The four horsemen of chronic disease according to Peter Attia:
Cardiovascular disease - mostly preventable
Cancer - somewhat preventable (smoking, alcoholism for example)
Neurodegenerative disease (dementia) - jury is out on this one but physical activity is shown to have benefits in this area
Diabetes - mostly preventable
There seems to be plenty of preventative measures one can take to improve the odds of relatively good health. Spend some time in a grocery store making observations of contents of normal weight people and obese people. Look who gravitates to the produce section vs frozen prepared/packaged food sections. Even brisk walks have tremendous physical and mental health benefits.
Outlive: The Science and Art of Longevity by Peter Attia, MD is a decent read if you want to educate yourself.
Outlive: The Science and Art of Longevity