over 1/2 lb of bodyweight per day? Some of them have averaged losing a lb per day! Say the average loss is 3/4 lb, and that some of that loss is muscle, not all of it being 3500 calories per lb (ie, fat). So they average losing 2500 calories per day). You can do better than that just by lying around in your sleeping bag. If that's all you do, an averaged size man will lose only 2000 calories per day and a small woman will lose only 1200 calories per day. If the woman is short and weighs 200 lbs, she can win without doing a thing.