Cal once did a metabolism check on 1,000 obese people and found out something like 95% of them had normal metabolisms. hell i should probably lose 20 pounds, but i don't blame genetics. it's booze and food and not enough exercise.
it's usually not hard to figure out why someone is that fat if you hang out with them. i have a friend and his wife that are both 100+ pounds overweight and we went to a buffet and she literally ate twice as much as i did and i'm a big guy. others will claim they don't eat a lot and then binge when they get home. there's this woman at my work who is always on a diet and eats salads every day but then puts at least 1,000 calories of dressing on these huge salads. it's not brain surgery here.