Vegan diets conjure up images of lean, healthy folks, happily chowing down on massive bowls of leafy green salad. And science backs this image. In a large study of 40,000 adults, conducted by Oxford University, vegans were found to have the lowest BMIs among any of their peers, while meat-eaters, not surprisingly, had the highest. But not every vegan sees the same results after cutting out animal products from their daily diets. Some don’t see changes at all, and some can actually gain weight. If you’ve made the switch to vegan in attempt to shed pounds, here’s what you might be doing that could be sabotaging your efforts. Reason 1: Your overestimating portion size Sure, vegetables, fruits, nuts, seeds and whole grains are healthy food our bodies require to fuel new cell growth, and regenerate healthy hair, nails and muscles, but we don’t need an infinite amount of these nutrients. The amount…