I lived in a homeless shelter for eight years (personal decision to greatly reduce expenses while paying off debt). The men in the shelter had one obvious thing in common: they were all very poor. But their weights varied greatly, from rail thin to morbidly obese.
For the purposes of this discussion, I refer only to the men who actually lived in the shelter; I’m leaving out those who just came in for meals. The men I knew best were the ones who lived there with me for long periods of time. I got to know them and observe their behavior. And I got to see a clear correlation between weight and physical activity.
The men with thin-to-average builds were the same men who would volunteer to perform physical labor around the shelter These same men were always the first to sign up when somebody called about hiring day laborers. These were the men who were hoping to pull themselves up and eventually stop being homeless.
The overweight men were the ones who preferred to perform the minimum amount of work that was required of them, who never volunteered, and who never went out to perform day labor. These were typically the men who ended up living more or less permanently in the shelter.
When meals were served, it was “all you can eat until it runs out”. There was no shortage of food in the shelter. There was no way for somebody to go hungry while living there. The first group of men would take what they could eat, and when they were full they would stop eating. The second group of men were always the first to get in line for seconds. If there was still food left after seconds, they would get in line for thirds. They didn’t stop when they were full; they would only stop when there was no more food.
It was an interesting contrast to see a thin man come into the shelter who had been on the road for a few weeks (I speak of an example “thin man”, not a specific person I saw), and had had very little to eat in that time. He would arrive very very very hungry. You would think this guy was an ideal candidate for hoarding food. Surprise! He would eat ravenously for the first few days. But after a few days, his great hunger would be sated. From then on, he would eat only what he needed. His weight would not dramatically increase over time.
By contrast, some men would arrive at the shelter perhaps noticeably overweight, but not obese. Like the thin man above, they would stuff themselves for the first few days. But they wouldn’t stop after the first few days. They would continue to stuff themselves at every meal. It was as if, no matter how long they stayed at the shelter (some of them for years) they just couldn’t get it through their heads that there would be another meal in a few hours. They had to eat as much as possible at this meal. And then eat as much as possible at the next meal. And the next. And the next. There were always desserts (cake, pie, donuts or candy donated by local grocery stores) left out on a table between meals. These men would take entire pies back to their rooms and eat them in one sitting. These men would just get bigger and bigger. I used to watch one man – who must have weighed close to six hundred pounds – regularly go to the dessert table and shovel handfuls of candy into his backpack.
What I’m getting at is that there is a lot of personal choice involved. The thin man and the fat man in the shelter have identical available options about what to eat. One man chooses to eat what he needs and maintains a healthy weight. The other man eats more than what he needs, and gains weight.