What exactly is the Slim Fast plan?
It's not so much that I hate the idea of anyone following the SF plan, considering I don't know much about it. From what I know though it's a bunch of shakes and bars and that's no way to eat long term... as you stated.
So if you want to start with it, great. If that's what keeps you motivated to stick with it. But eventually, I think you'll have to start reprogramming your brain to eat healthy, balanced meals that you enjoy. Without leaving the rigidity of a structured diet plan, you're really setting yourself up for failure. That's a blanket statement not really directed at you based on my own experiences working with people, so take it for what it's worth.
Let's not forget that anything works assuming by work we mean weight loss. Anything that controls calories works. There's nothing magical about SF over whole, natural foods.
Of course there's more that goes into successful dieting than calories... but that's the 'primary fundamental' if you will.
And I'm not trying to change your mind about anything. Just want to make sure you have all the information so you can make the best decision for YOU.