All right, before I start talking about fat, I want to talk about a little economic conundrum. So bear with me; it's relevant.
So, there's this island. We'll call it, say, Nes, for the sake of expediency, but its name isn't important. Now, the island's dwellers survive by getting regular shipments of supplies. Because of unknown circumstances, these shipments are always exactly the same--the contents never change, although the frequency can alter according to the islander's needs. Within each shipment, there is a particular necessity that comes in red boxes. No matter what, the shipping company can only send six of these red boxes per shipment. Now, that's okay, because that's all the islanders need in proportion to the other stuff they get, so nobody's got a problem with this.
However, the shipments start arriving with less than six boxes. They have the same amount of everything else, but they show up missing some of those red boxes. They complain to the shipper, who responds by saying that the shipments leave their port with all six boxes. "Okay, but we really need more red boxes," the islanders say. "Then you're going to just have to order another entire shipment to get the boxes in it," the shipper responds. They don't have many options, so the islanders increase the frequency of their shipments. They get half as much of the red-boxed stuff as they need, which means they have twice the amount of other stuff--an amount they cannot use.
Well, what would you expect these islanders to do, exactly? Throw away the extra stuff? Or store it, in case the shipments are short on those items at a later time? So they store it, and store it, until the warehouses are crammed full, and everyone has an attic crammed with it. And then, they have to build docks and floating warehouses to store it all, because they don't want to throw it away.
Along comes a guy, however, who says, "I think I know exactly what your problem is..." He points out that, for the time being, they can slow down their other shipments, and order just the red boxes from another source. However, that's a short term solution--the real problem is that, en route to the island, pirates are attacking the ships and robbing them of the red boxes. They don't take all of them--if they did, then the shipments might stop entirely until the pirates are dealt with--but they take about half. The real solution is to eliminate the pirates so that regular shipments can go through unmolested.
So, that brings me to our malnourished 300-pound woman. We'll call her Myra. Myra is a big woman, and she is very hungry, all the time. She also has skin problems, her hair's falling out, and she feels tired and sick a lot of the time. Lots of doctors have told her to stop being such a fatty mcfatty moo cow. Stop eating so much, exercise more! But the hunger is unbearable, and her fatigue is crushing. Myra gets sick and tired of her doctors having no real help to offer her, so she does her own research and finds some doctors that have compassion and the ability to see and hear patients, due to NOT having their heads rammed up their rectums.
Myra and her medical team finally figure out that she has severe auto-immune problems, including some nasty food allergies. Basically, when she eats gluten, her digestive system becomes so inflamed that it cannot properly absorb many of the nutrients she eats--but does allow the calories to be taken in and stored. Because she is low on vitamins and minerals, her brain sends out FEED ME signals that drown out pretty much any semblance of sanity she has. So she eats more--and the calories get absorbed and stored, while the vitamins and minerals pass right on through her ravaged system.
And, the previous solution to this has been, don't eat so much. For someone who is literally starved--not of calories, but of other nutrients--this is a cruel thing to prescribe.
So Myra, now that she has sorted out her food allergies (and hypothyroidism at the same time; autoimmune stuff is harsh), she takes a megadose of certain vitamins to "catch up" until her body has recovered enough to get enough of those things from the food she eats. She's finally recovering, and, surprisingly to her, the stored calories are now being utilized as her body balances itself and goes down to her natural setpoint--through no effort of calorie restriction at all.
I haven't even gone into the biochemical feedback loop that creates even greater cravings (inflammation -> adrenalin -> hunger), but there is quite a bit going on that most of us don't even realize or think about. It's awfully easy to point fingers at someone for eating "too much" or being too sedentary, but unless you have lived inside that person's body, you have no idea what their situation is like. Mistreating someone for being hungry, fat, or sedentary is arrogant and ignorant--and it doesn't do anyone any good. If you truly want to help people be healthier (not "lose weight", but "be healthier"), you should advocate for better education about things like hypothyroidism, celiac disease, and other things that can create situations like Myra's. If you're not interested, however, then learn to mind your own business regarding other people's health and bodies.