The thing is that once you get your diet and exercise routine right 'for you' then the issue of how to keep it up goes away. It's so self-reinforcing that you would be hard pressed NOT to eat and exercise well.
The hard part is getting it right for you. I like to run and I've run my whole life so exercise was never an issue, guess I lucked out there. I've tried going to a gym many times and it just is not for me, for example.
Whereas it took until my 50s to figure out that a low-carb diet was right for me. Before I had a terrible sweet tooth, but now you couldn't pay me to eat sugar.
So my advice is to try lots of things without getting hung up on the dogma associated with each, until you find the things that click.