Hell, for a normal weight person a 2-5 lbs fluctuation in weight from day to day can be totally normal, depending on carb and sodium intake, among other things. For a gigantic fatass, 10 lbs is probably the difference after they take a huge dump. If they don't look or feel any different, the only point is to get fake accolades and pats on the back, so they can feel better about themselves as they continue to gorge on junk.