BasilBoy wrote:One other point: if we are going to look at our distant ancestors to determine what's best to eat (which I think is a mistake since our food choices are completely different today), we ultimately evolved from herbivores. There is absolutely no reason why we couldn't evolve back into herbivores...
Well, maybe in a few tens of thousands of years... maybe. But evolution is not the same as some ascetic changing their diet and spending most of their day meditating.
Evolution gave us a body equipped to eat meat and most importantly animal fat. Without consciously selecting a very specific diet, you will not achieve a zero calorie balance that excludes both animal and processed foods. A good sized, active male would have to eat a continuous stream of nuts; maybe some could stand it, but it would get old fast.
Could a slim, sedentary female make it work without losing weight? Probably. Maybe an office dwelling, small, commute by car male. Or an exceptionally dedicated larger human willing to eat enough nuts every day, forever... :-<
When someone says "vegan" to me, I tend to think of what I'd have to do to get 3500 Cal/Day. But I always end up with the same conclusion: I can't eat that much. (and 3500 Cal/Day is really not very high on the activity scale; a couple hours or so at 75% output will easily put many past that mark)
So.. Challenge to Vegans:
a) show me a 3500 Cal/Day plan that a human can manage to eat every day. forever.
b) show me a menu that can make up for a 5000 Cal day expenditure.
I don't really mean any offense by this, but Veganism is designed for office dwelling hominids who's typical trip to the gym involves walking around, talking, and getting their heart rate to 65% for 3 minutes, followed by a shower and three hours of TV. This is ok, and maybe that's where we'll evolve to, given enough singularity derived energy; but its not what we are now.