One of the reasons you can drink so much caffeine on Tim Ferriss' Four Hour Body Diet is that there aren't any carbs or sugars in it. Tim loves coffee, as do millions of other people. But this doesn't make it good to drink. Tim also loves his diet coke. Which is completely ridiculous for someone purporting to follow a healthy lifestyle.
You might lose weight on the 4-Hour Body Diet, but you're not necessarily going to be in complete health. The meat issue is central. Check out sites like Slow Carb Vegan that try to follow the slow carb diet without meat. I think that if you can combine the slow carb idea with other diets like Joel Fuhrman's Eat to Live plan, you'll be better off.
Stopping caffeine, you'll be better off, too. Thankfully it's not as bad as cutting out sugar, which is in everything. You need to get to a place where caffeine is not an emotional crutch for you, where you don't feel psychologically like you need it anymore.
The fact that Tim still relies on diet Coke (full of caffeine) and coffee makes some of his other choices suspect for me. I think he got to a place where his diet worked for him, so he stopped questioning aspects of its health. When you think about it, what's your intuition? Is diet Coke healthy? In an ideal world, should you really be drinking it? Diet Coke might as well be full of carbs, since it all breaks down into glucose anyway. There's no glucose in coffee, but it's still going to mess you up.