Anciently, during periods following famine (and also, at the harvest), there followed periods of feasting and celebration. Understandable.
What do people do, when feasting? Overeat. Consider Thanksgiving.
Now, that's not the end of the story; it's where something new makes it interesting.
What happens to the size of the stomach, when we overeat? It enlarges.
And what happens to the abdominal cavity, as the stomach enlarges? It enlarges, to accommodate.
And what happens when the abdominal cavity enlarges? The muscles of the abdominal wall relax.
And what happens when the muscles of the abdominal wall relax? They make room not only for food, but for the additional blood circulation needed needed for the stomach to digest all that food (particularly, the proteins).
Well and good. Sounds healthy.
However, what happens when a person habitually overeats? The muscles of the abdominal wall come to stay habitually relaxed.
And what's below (or just interior to) the abdominal wall? It's called, "the greater omentum". The greater omentum is a body of fat that drapes, like an apron (apropos) over the abdominal organs.
And what do you think happens to all those nice, juicy nutrients from habitual overeating, with habitually relaxed abdominal wall muscles and all that increased blood circulation and with the greater omentum nearby, through which some of that circulation circulates? By George! That greater omentum, which has lots of nice space around it, is just waiting for all that nice excess nutrition to fatten it up. The body adapts to our way of life and changes shape accordingly; ask any fitness nut. We become how we live.
The fault doesn't lie with the greater omentum.
The fault doesn't lie with the increased circulation.
The fault doesn't lie with those relaxed abdominal muscles (that everybody wants to tighten).
The fault doesn't lie even with all those nutrients.
The fault lies with the fact that the person habitually eats too much at one sitting.
If (s)he ate less, the stomach would not enlarge, so much, the abdominal wall would not distend as much, and there would be less room for the greater omentum, and less circulation. And less belly fat gain.
After times of famine, it's understandable that people might feast. And it seems somehow "naturally sound" for people feasting after famine to get fatter -- as a way of "putting somthing away" in case of future famine -- a protective evolutionary development.
And in fact, what has been observed is that people who starve themselves to lose weight end up gaining more weight, than before, after the starvation diet ends. That's one reason why it's being said, "Diets don't work." It's the evolutionary program for famine.
Maybe I've just described more about how that works -- and why it's better to eat many small meals and snacks than it is to eat a few large meals -- as, in some people's case, one big meal each day.
Now, it's also understandable why some people overeat. Famine is a "stressor". And under stress, our belly wall does tighten ("Startle Reflex"). Feasting after fasting is a way of relieving that stress and also of forcing that tight belly wall to relax, simulating relief from stress.
Does the nature of the stressor matter, when it comes to relieving stress? Do we really differentiate one stressor from another at the feeling-level? or do we just go for the all-purpose stress-reliever, the traditional one, the ancient one, that one that was appropriate after the stress of famine (or deprivation) -- food.
Could it be, that is why people are seek to relieve stress by overeating? Why we might eat when depressed? or lonely?
And what does it say about our times?
Obesity is a symptom of a distressed society and of ignorance about stress and eating (including poor choices/quality of food/quantity).
Just a hypothesis.
"Never eat anything bigger than your head."
~~ R. Crumb
a few resources:
Somatic Breathing Training to Reduce Stress
The Cat Stretch
to reduce Startle Reflex