Stomach feeling full based on calorie intake

Question

In the world I am building I wanted to design a race on a planet which get more full the more calories they eat and then stopping when they have had their daily caloric requirement. I have an idea's on how they would do it physically (sample parts of the food going down their esophagus equivalent and estimating on the amount going to the stomach).

The problem I have is why this race would create this evolutionary tactic in their hunter/gatherer phase. If you find a bunch of berries you would eat as many as you can fit in the stomach, store excess calories as fat, and take the rest back to village for later.

I usually try to find a corollary examples for races I make from earth and I try to be at least a semi-hard on science as to why races are the way they are.

Any ideas would be nice.

Answer 1

Your race evolves under circumstances where overconsumption of calories is common and potentially dangerous.

A parallel is seen with salt. Salt is delicious and we need it. But if it were purely delicious and an individual happened into a big pile of it, it would eat it all and get sick and possibly die.

High salt recruits aversive taste pathways Yuki Oka et al Nature 494, 472–475 (28 February 2013)

By contrast, salty taste is unique in that increasing salt concentration fundamentally transforms an innately appetitive stimulus into a powerfully aversive one. This appetitive–aversive balance helps to maintain appropriate salt consumption and represents an important part of fluid and electrolyte homeostasis.

Suppose overindulgence in calories happens often, and there is an evolutionary price that outweighed the benefit of storing away calories for hard times ahead. What could that price be? Refeeding syndrome can happen to people in concentration camps - they are starving and then when they are given all the food they want, electrolyte levels crash and they get arrhythmias or stop breathing. Maybe your race is prone to something like that.

An alternate bitter receptor for high calorie (like for high salt) seems tricky. A different way to evolve stopping when you are full is to make the stomach smaller, like people who have stomach reduction surgery. Or just attribute their satiety to their genetics: the sensation of being full is evolutionarily flexible and under genetic control. https://www.gbhealthwatch.com/GND-Obesity-MC4R.php

One could make a case that humans are already set up as you specify - to stop eating when they are full - of fat. The obesity problem now is due to easy availability of carbohydrate calories, which make an end run around a mechanism that evolved in a time where the only way to eat an immense amount of calories was by eating animal fats. Ketogenic diets work in part because fats are filling in a way carbohydrates are not and people get full and stop eating.

Answer 2

There is no known scientific rationale for what you want to happen. Living creatures do not have a "daily caloric requirement." Instead, they maintain their existence by adjusting their caloric output according to what they bring in. If you don't eat enough, you shut down less essential parts. While the US government may recommend 2,000 Calories/day, we can operate on far fewer. As we get near 1,200 Calories/day, our body starts to shift gears to conserve more and more energy. As we approach 500-800 Calories/day, our body will start to shut down bodily functions to preserve energy to support the lower regions of the brain. On the flip side, you have Michael Phelps, who ate 8,000 - 10,000 Calories/day before the Beijing Olympics. There, the vast majority of his caloric intake was expended in his practices.

This flexibility is incredibly important from an evolutionary perspective. Food supplies are never reliable. If you can't scale your output to match your input, you will die and be replaced by a species that can. There is no known species that doesn't engage in this sort of flexible operation. It's fundamental to how life as we know it functions.

To come up with a species that doesn't have this, one is going to have to reach well beyond realistic science. Consider the Octospiders from Clarke's Rendezvous with Rama. That species is a highly advanced species with many peculiar traits. One of them is that they have to be taught to recognize the feeling of hungry. Their babies are born with a truly blank slate, and one of the first tasks of the nursery technicians is to teach the babies to eat before they starve just sitting there.

In such an environment, one might have "daily caloric requirements" in the form of instructions dictated to you. You may consciously be aware of the food you eat and stop when you reach the level dictated by your society.

Answer 3

What kills people?

On our world we have gone hungry fairly often, and starving still is a fact of life in many parts of the world. But if there has always been enough to eat something else would bother them.

Say like Eloi they had all the food they cared for always available, perhaps overeating or having excess fat would be a major problem.

If to escape predators they typically hide in tight places, there is some poison common in their environment that could accumulate in fat or the stable food supply wasn't fast replenishing and was easily damaged by over harvesting, limits of consumption may selected for.

Answer 4

Body fat is a very efficient way to store extra calories on living creatures. Unfortunately there is not an equivalent procedure to storing water, This is interesting as water is just as important for life but it can actually kill some people when they over drink.

What if, we turn off the ability to store extra calories in the same way. All the sugars you eat would go right to the blood stream, thinning out your blood. The more your people eat the more "light headed" they would feel, as they wouldn't be getting enough oxygen.

The lack of oxygen would be a natural way for your species to know they are over eating. Unfortunately not having access to body fat would create a number of other issues.

You would also have thrill seekers who would eat to much high caloric foods just for the weight less feeling they get.

Answer 5

This is not as hard as it seems.

Take away the evolutionary advantage of storing excess calories. One way to make sure that this evolutionary trait never developed is by making your species always having had an abundance of food. For example your species is rather small compared to many herbivore animals that they could effectively hunt (with poisoned spears). To top that off, maybe they have a good way to preserve this meat.

If food is pretty much guaranteed to be available at any time, but people still had to eat to survive, it would make sense that people would still enjoy food and have an evolutionary impulse to eat, but not to overeat, which in the end does weigh you down, is time-consuming and potentially harmful when food is spoiled.