Why do humans have a preference to over eat or over indulge and not just be satisfied with what is needed to sustain their life and health?
In: Biology
Humans evolved to live in a pre-agricultural world. They live in a very different one, where food is industrially developed and processed. Behaviors, like eat every berry you come across, made sense before, but not today.
For the vast majority of human history (history of all life, really) food was scarce and you spent most of your time just trying to get enough to eat. When you were lucky enough to have _too much_ food, overeating let you pack on the fat that would keep you alive when food _wasn’t_ plentiful. Folks that didn’t overeat during the good times starved to death in the lean times.
It has only been the last 100 years or so that food insecurity has ceased to be a prevalent issue in the Western world. You and I aren’t worried about not having food to eat tomorrow. The problem is that the instincts that kept us alive for hundreds of thousands of years are still there, so we are hard wired to overeat even though we _know_ there is no reason to.
Because almost everywhere and for almost all of history, “Enough to eat today” has been no guarantee of “Enough to eat tomorrow”. So the people who survived – our ancestors – were the ones with a tendency to eat what they could, while they could.
Biologically, it’s not in your best interest to only take what you need to “break even” with what you spend. Currently, most of us (in the wealthier side of the world) are in a constant state of plenty, where eating until we are satisfied is both the ideal scenario, and the one we have access to pretty much at all times. For this group, going days without food or skipping meals is a choice, not a requirement to endure.
Your body is evolved around the idea of not having times of plenty every single day, however. The days you overeat or take advantage of a resource today, help make up for days (tomorrow, the day ofter, or so on) where you can’t take in everything you spent. Our bodies store energy by necessity, rewards high-energy food sources to make sure we are encouraged to seek low-cost rewards to maximize our chances (less energy spent seeking food is better), and so on.
It’s made all the worse because we have access to all of these in abundance, and they make food all the more enticing, and hard to cut back on. Ironically, over-indulgence is a new danger to our health when you are wealthy enough to afford choosing your meals every day multiple times a day.
No animal is satisfied just eating an amount that they need to sustain life. It would mean that they’d have no excess stores and would begin starving as soon as food was unavailable. Every animal has evolved to eat a lot when food is available in order to account for the times when food is unavailable.
Today’s food in the developed world is often full of sugars, fats, and salt and tastes damn good! We eat it for pleasure more than sustenance and, like anything that gives us pleasure, overindulge and addiction can become a problem.
Because “an unhealthy amount of calories even being an option” just wasn’t a thing for like 99.9999% of evolutionary history. Food was scarce and unpredictable for thousands of generations of our ancestors, and there was always the threat of drought, injuries, sickness, etc. so **”eat all the calories you can find” was the optimal strategy that evolved.** That worked great since it was basically impossible to regularly find and eat enough calories to be a problem.
All of that changed only about 100 years ago, with calories suddenly being easily available all the time. 100 years is a fraction of a blink of an eye compared to the speed of evolutionary adaptations. It’s just WAY too recent a change, and so we’re all still running the “eat all the calories you can find” program since that served the last billion years of ancestors really well.
When our ancestors were living in the trees, those that gorged themselves when food was available were more likely to survive when food was not available, and these survivors would go on to have more babies, and those babies would be more likely to inherit whatever it was about their parents that made them want to gorge themselves when food was available.
We have not significantly evolved as a species since that time, despite civilization rapidly changing and for many people eliminating food scarcity.
Because we haven’t had time to out-evolve our hunter-gatherer instincts.
We’ve only had what you could call, for want of a better word, civilization, for maybe 6,000 years, agriculture for maybe 12,000 years.
For the other 95-98% of time that humans have existed as humans, we were hunter-gatherers.
When you’re a hunter-gatherer, you don’t have much in the way of stored food, you don’t have a harvest you’re expecting or a granary, or a pen full of sheep you keep for wool, but could slaughter for food if times get lean.
You *don’t know* where your calories are coming from tomorrow, so **you eat whatever you can as much as you can TODAY.** Back then, those impulses served us well. Storing up some extra calories in good times could make the difference between surviving a lean season and succumbing to starvation and disease.
Having a relative overabundance of cheap calories available is an extremely recent phenomenon. Even in “civilized” countries, it’s only become common in the last 50-100 years. Before that, mostly only the wealthy and powerful could afford to become fat.
So… even though you know you have all the calories you need, you’re still attracted to calorie-dense foods, as much as you can get, and it takes a lot of effort for your nice modern forebrain to overcome those impulses.
This is especially true if you grew up poor, in a situation where you *didn’t* necessarily always have enough to eat. It tends to kick those instincts into overdrive, and they stay with you into adulthood.
Because the food we eat is over-processed and engineered to make us crave it. It also has way more nutrients and calories than the food we used to eat.
Combined with lower amounts of physical labour, our bodies hormonal systems get disordered and we lose the ability to regulate our food intake properly.
Contrary to what others are saying, there were many human societies that did not have a lack of food.
For example, prior to WW2, the Netherlands had not had a famine for centuries.
Multiple generations of humans grew up with more than enough food.
The nutritional value was lower, which is why people nowadays are taller and fatter than back then.
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