I'd like to draw your attention to a guy who goes under the Youtube channel as Second Chance Fatman. I think around 500 pounds at his heaviest he has used a plant based diet to reduce his weight with increasing energy and no hunger pains. Right now he has reduced his weight by 150 pounds, so I think that means he now weighs around 350 pounds.
youtube.com/watch?v=r7JLiik... is his first video and youtube.com/watch?v=LHYHLcv...