Yeah, what @gettingfired said! Don't know this Dr. Greger but personal experience says vegetarian/vegan diet + intermittent fasting = slim person.
Every body is different if course, but it works for me. Plus, I don't believe I've ever seen a fat vegan :)
the only way i've ever losT weight is high protein/low carb regimes ($$$), and my previous attempts at veganism have only resulted in weight gain (no junk food) but i'm willing to stick to this for a while, till i find the formula