Without even worrying about the details of the recommended diet, I think you've got to ask the chicken-and-egg questions.
People who care about themselves and respect the need to look after themselves are, surely, far more likely to have a healthy diet to begin with than people with low self-esteem.
Likewise, smart, hard-working people are financially better able to look after themselves and are more likely to come across good dietary advice and good role models than (let's be blunt) dumb, lazy people.
So ... which factors are causes and which are effects? Or is it just one big snarl of problems for some people, spiralling down into poverty, illness and depression and (legal and illegal) drug abuse?
If you look at the people turning up at Casualty at your local hospital for non-accident reasons, you would certainly be inclined to come to that conclusion.