Couldn’t our biological organisms just prefer the healthy food? It would give us larger chance of survival so genes preferring healthy food should be more popular.
In: Biology
Whole foods are not “healthy” or “unhealthy”. We like fruits, we like meat, i.e. we like sugar and fat and protein. There’s nothing inherently wrong or “unhealthy” with those.
One problem with the modern world is that we have all foods in abundance, basically unlimited amounts.
The other problem is that we can make processed foods that contain a lot of fats and sugar, and are made up mostly of unsatiating simple carbs, and are nutritionally poor. They trigger our craving for fats and sugars without providing enough nutritional quality or satiety, so we tend to overeat on nutritionally poor junk, which is what makes us unhealthy.
Our brains and their responses to foods aren’t really changed from the days of early hunter-gatherers. We need various amounts of fats, sugars, proteins etc to survive, and when we find a food that’s rich in one or more of those our brains respond positively and encourage us to find similar things again.
Unfortunately, unhealthy foods feature so much fat and sugar that it completely overdrives the response. Our brains don’t get the concept of “this is too much of this nutrient and it’s actually bad for us” because they also don’t get the concept of “we’re highly unlikely to be in a position where we don’t know where our next meal is coming from”.
So the “thinking” of our brain is that every meal is critical, and more nutrient = better. So you eat bacon or chocolate, and our brain goes “oh god yes that’s the stuff!” and floods you with dopamine. And then you try to get that same dopamine hit by eating more unhealthy foods.
We’ve evolved to respond to certain cues from our food, not to the food itself. For example, you don’t crave “simple carbs to use for high speed running.” You crave something sweet, which in our ancestral environment is a cue that the food contains simple carbs. We enjoy fatty foods for the same reason, and those containing protein as well: calories we need. And for most of our history, more was better, because there was rarely enough.
In the present day, we have engineered flavors that are much stronger stimuluses than than what’s in nature. In nature, ripe strawberries are sweet and we enjoy them. Nutella is like a thousand times sweeter. Your gustatory system doesn’t know that it’s artificially engineered and not nutritious. It doesn’t know it doesn’t need to stock up for the future. It just knows “wow, this must have so much of the nutrients I need.”
Now, if you project out over millions of years, is it possible humans slowly evolve a preference for more nutritious foods? Yeah, it’s possible. It’s not likely – we might be stuck on this path – but you never know.
It’s because there are about a million food scientists that load up the processed food with all manner of flavors that we love. Many processed foods are literally designed to appeal to our taste buds.
We have caveman brains. A caveman brain still expects the food to run out.
Unhealthy food tends to be fatty or calorie dense. If we eat calorie dense stuff, we get **lots** of fuel for our bodies all at once. We get fat, and then when there isn’t any food we can use our fat to live off. Caveman brain gets excited by fatty, calorie dense junk because it’s a lot of fuel and means that food running out a month from now is less of a problem
The larger chance of survival often means getting more of what you need to keep going, and consuming food that is rich in nutrients rather than nutrient poor.
“Unhealthy” food often refers to things that are just very *dense* in these things, so over-eating frequently or unbalancing your diet towards *one* of the groups of nutrients you need and not the others (such as high fats/oils, or sugars, commonly) is easy. Our bodies store things if we take in more than what we need, so if we are regularly consuming foods dense with calories, we are storing that excess again and again repeatedly, without burning it away or using it at an equivalent rate.
That + potentially missing those other nutrients and diet components you need is what makes it unhealthy. The food themselves are rarely the issue, it’s in how you moderate and balance your intake.
Define “unhealthy”.
If we eliminate highly processed foods from the definition then mostly what we’re left with are sweets, alcohols, and other similar indulgences. But are those things actually intrinsically unhealthy?
Our bodies require carbohydrates to survive, so sugars in moderation are a necessity. Alcohol in moderation improves a host of chemical activities in the body including cardiovascular health.
Again, define the word unhealthy. It can only mean “in excess” because it certainly doesn’t mean the food itself.
ELI5: because historically, overeating was not a problem. Cavemen weren’t worried about getting fat from eating too many calories, they were worried about dying from eating too few calories. So we grew to prefer foods with higher calories, which are foods higher in fat and carbohydrates and protein.
Our bodies don’t know what is healthy versus unhealthy.
Evolution is a long process. Many of the traits and behaviours we have now aren’t “human” behaviours, they’re “mammal” behaviours. You may even hear talk of the “lizard brain”. We have as part of us, the remains of hundreds of millions of years of evolution. Chemical processes which may not make much sense in a human in 2024, but made perfect sense in a small monkey 1.5m years ago. Or in a fish 400m years ago.
Mammals in general tend to prefer high-energy foods over nutrient-dense ones. Foods from which you can extract a lot of energy relatively easily therefore give you an overall competitive advantage compared to someone eating foods which require more effort. Plus, for most of history, food has gone through periods of availability and scarcity. So we have evolved a mechanism which encourages us to eat as much as possible now in order to prepare for an inevitable upcoming scarcity.
Thus, we show a general preference for foods with a higher carbohydrate & fat content, as these will allow for more energy to be extracted. Of course, this has never been a problem. High carb foods usually comes with a lot of nutrients attached. And high-fat foods usually come with a lot of protein attached.
In modern times, what capitalism has managed to do is short-circuit this. Produce food that’s both high in carbohydrate and fat, but low in nutrients. The concentration of energy in this food is way more than you will ever really find in nature, so our brains have no real “guard” against this. All our bodies see is mana from heaven, and we are driven to consume as much as possible.
By default there is no healthy or unhealthy food, unless you are talking about literal poisons. You need a balanced diet with the right amounts of each nutrient. This does mean that you do need some sugar in your diet but not too much. And you need some salt in your diet but not too much. Humans have evolved to crave foods that are hard to come by. So when there is not much food available you would eat the most energy dense and the food that gives you the most important nutrients first.
But as food have become more available you tend to get too much of this food, making it unhealthy. We can even see this change in our lifetime. The food pyramid from the 1960s had carbohydrates like bread, pasta and potato as the staple food that you should prioritise. And this was good advice at the time because a lot of people did not have enough money for a full diet. Carbohydrates was a cheap way to get enough energy. If you are hungry and only have $10 to spend at a fast food place then you should get the fries and not the chicken. But if you have enough money to buy anything you want then a chicken salad is much better then fries.
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