I tried a vegetarian diet for years living in California and I personally felt awful. I didn't think it was related to my diet, but eventually that's the only thing I could correlate it to. Surely it's because of the high use of soy, Stevia, and other garbage that my body does not tolerate well, but I was getting severe stomach problems. I was always hungry and I could never get full enough, and yes I tried a ton of different foods. Once I started eating a little bit of meat again (beef or turkey like once a day) the problems disappeared.
I hear the best diet is the one that your ancestors ate, and I can vouch for that because my family's cooking style has always been traditional. Since switching back to a diet that resembles it more I've been doing a lot better. Acknowledging that culture actually influences your lineage's DNA over time (this has been proven), it makes a lot of sense. I'm also not talking about Paleo (although some elements of this have overlapped for me with this approach), I'm saying eat mostly traditional German food if you're German.