Without entering into a discussion about various diet "plans" like the orange juice diet, the California Spring Roll Diet, the eat a bucket of liver every day diet, ad nauseam, if you know any really seriously fat people, one thing you'll notice is that they eat just about constantly and what they do eat is in massive portions.
For example there are 3 real fat people (all under 30, all over 120k) in the SWMBO side of the family and they all have in common:
When attending an all you can eat buffet at pub or club, although they are free to make as many trips to the bain maries as they wish, their plates are nevertheless piled to overflowing at the first trip. Then the second and third. I have trouble just finishing one plate of the schnitzel, chips and rocketty salad stuff on Schnitzel Night.
When you drop in on them for a visit they always seem to be chewing on something right at that time and it's often weird stuff, like a whole packet of lamington squares or half a loaf of bread smeared thick with marge and slices of banana stuck onto them, almost like they are taking medication.
Lunch is more often than not a full sit down feast at a Thai restaurant, or an upsized Hungry Jacks Double Whopper, large fries, large onion rings and large coke. Which comes to around 3500 cals if I'm not mistaken. And that's just a snack to see them through to those lamingtons etc.
Now I'm not going to get obese, just looking to take off maybe 9 kg and I'll be good. But it does strike me that people who are obese seem to have a huge food capacity - maybe they just have huge stretched stomachs that have to be filled to trigger the "I'm full" hormones that get triggered in most of us when we eat far smaller quantities?