I was a low-fat vegan for years, on and off. It's hard enough to be vegan but without fat (cooking oils, nuts, avocado, coconut, even tofu) it really does not work. I followed the McDougall Plan and my goal was weight loss. I lost weight but ended up relying on bagels and pasta to get enoough calories. I am a firm believer after that experience (and attempts to eat raw-food only diets) that we will get our calories where we find them, and are meant to be omnivores.