Not entirely true...I'm kind of bouncing back and forth between my diet (which works very well) and just trying to eat healthy. My habits haven't changed enough yet to not sabotage myself. This attitude is my goal though ;)
It's basic ecosystem science. Every time you go up a tropic level 90% of the energy is lost. So eating lower on the pyramid is more sustainable. Especially when you take into account the amount of fossil fuels it takes to raise meat.