I understand food wasn’t always so abundant, and humans were well served to store excess consumed energy as fat for later use. What I don’t understand is why the body keeps storing fat to the point where a person becomes morbidly obese and it puts their entire health at risk. Why isn’t there a point where the body just let’s the extra calories pass through without saving for later?
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That situation just doesn’t come up in the wild. Food just isn’t plentiful enough for *not* storing everything available in case of famine.
Evolution doesn’t prepare us for situations our ancestors never experienced.
(edit to add word my stupid fingers deleted)
When your body runs out of energy from sugar/carbs/ etc. it uses the fat to pull energy from. There was a long time where those things were hard to find so we stored fat to make sure we can get through times of drought or famine. Getting fats and sugars have become easier to get and evolution hasn’t caught up
Edit: typos/missing words.
Our technology has outpaced our evolution and we can easily consume more calories than was ever possible to consume before about 50 years ago. The worst part is that we crave it because millions of years of evolution has programmed us to feel like fattening up is an advantage to survival.
For the most part, animals don’t have a mechanism to just magically “burn” excess fat. And that’s because in a natural setting, most animals struggle to accumulate food, not struggle to shed excess weight.
The excess weight part is generally solved by a lack of fitness which means increased chance of being injured/killed by predators.
Humans have no natural predators which eliminates that issue.
An oversimplified answer, but the calories, carbs and sugar you consume have to go somewhere.
If you are doing activities that burn a lot of calories, it can help increase your natural metabolism to burn calories fat naturally, but it either has to be burned or stored.
You are what controls whether you are consuming more than what your body needs. Your body just deals with your decisions as best it can.
It generally won’t and doesn’t if you don’t live in an industrialized society. Getting fat to the point of negative health impact is a feature of life in an industrialized society, every society that industrializes sees their people lose the ability to regulate their fat levels, and it’s likely the result of “obesogenic” chemicals we’re exposed to in such an environment.
I think the best way to understand why is to start with the fact that storing excess glucose as fat isn’t an actual decision in the first place. It’s simply the result of chemical reactions. Many innate behavior patterns are pretty much just the animal taking advantage of what chemical reactions their body is capable of performing.
So to answer your question, fat will continue to accumulate because there is no mechanism to stop it if there continues to be excess carbohydrate consumption. If blood glucose is above a certain level in the vessels that pass by pancreatic beta cells, insulin is released. Insulin in the blood above a certain level blocks glucagon release. If there is no insulin, then glucagon is constitutively released. Insulin triggers a series of reactions that lead to eventual production of fat. Glucagon leads to breakdown of fat into more glucose. Notice how this system doesn’t leave any room for simple excretion of the excess.
To add on to this, normal kidney function at normal blood glucose leads to complete retention of all glucose (it gets filtered out of the blood into the nephron and then reabsorbed down the line). You do end up with (Edit: ~~urine in the blood~~ oops) sugar in the urine if you have diabetes as the reuptake transporters get completely saturated. But this only happens because the normal balance between insulin and glucagon has been disrupted. We would also rather have normal insulin function than this because excess glucose can be very damaging, including things like kidney disease, eye disease, nerve disease, etc. High blood sugar will directly kill you so blocking the effects of insulin for the sake of stopping fat production is not an option.
Lack of a need for the mechanism to exist relative to the selection pressures of evolution. It would require a population eating itself to death due to abundance before its members could reproduce.
Because we never needed that. For *millions* of years, the strategy that worked was “eat all the calories you can find”. And that only became a non-ideal strategy like 50-100 years ago. So we’re all still running the programs that served the last 1000 generations of ancestors really well, up until like 2 seconds ago in evolutionary time when calories became cheap, easy, and everywhere.
There isn’t really a way for food to “pass through”. If your body doesn’t burn it or store it then you’ll have sugar and fat building up in your blood to the point where it kills you very quickly.
There is a circumstance in type one diabetics who don’t take their insulin where fat builds up to the point where their blood gets so thick that it’s like custard and often times their sugar levels reach over 1000. This is essentially what would happen if you didn’t store or burn your food.
Another interesting point that is slowly being worked on is inhibiting an enzyme that processes sugar. This method has been used in mice successfully but not humans yet. The enzyme “fructokinase” breaks down sugar so your body can use it as fuel and inhibiting this enzyme in mice caused them to pee out the sugar and they lost weight as a result. The implication of this in humans,if they can pull it off, is it would be very helpful for diabetics in managing their blood sugar, but could also reduce non alcoholic fatty liver disease considerably in people with a high sugar diet as well as contributing to weight loss. Like I said, this isn’t possible yet, but it’s the closest thing to what you’re asking about.
The problem at the moment is that it is in your body’s best interest to accept all calories because it evolved in a time when food was hard to find and it takes a long time for evolution to take effect. The better solution would be for people to stop eating processed food but that’s just not going to happen. And if the body did evolve to let your food “pass through” and a famine hit, a shitload of people would die because they wouldn’t be storing food as fat anymore and it would be much easier to starve to death
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