The need for love and intimacy is a fundamental human need, as primal as the need for food, water, and air.
When you grow up in an extended family, or in a stable neighborhood with two or three generations of families who live there, you feel seen. Not just the good things you've done, the stuff you put on your resume. You know they've seen you in your dark times, when you've messed up - but they're still there.
Because the biological mechanisms that affect our health and well-being are so dynamic, when people change their diet and lifestyle, they usually feel so much better, so quickly; it reframes the reason for changing from fear of dying to joy of living. Also, the support that patients give each other is a powerful motivator.
There's no point in giving up something you enjoy unless you get something back that's even better, and quickly.
Think about it: Heart disease and diabetes, which account for more deaths in the U.S. and worldwide than everything else combined, are completely preventable by making comprehensive lifestyle changes. Without drugs or surgery.