Why on Earth do most people enjoy unhealthy food?

Question

I know some people may argue: "I actually love eating unsalted tuna with broccoli", but the sad truth is that most people don't. If I had to choose between a cheese burger with fries and unsalted chicken breast with carrots, I would certainly go for the burger. I bet most people would do the same, at least statistics say so.

My question is: why do our brains prefer unhealthy, fat, food instead of healthier food such as steamed vegetables and some sort of meat? Are there some evolutionary facts that make us prefer this kind of food?

Answer 1

We evolved to find calorie-dense foods very tasty, and we don't have taste-receptors for micro-nutrients

When humans (and most of their predecessors) did most of our evolving, low-calorie plants were plentiful. Sweet fruit wasn't usually around all year. Meat could be hunted, but it required plenty of energy and effort, and was usually quite lean. (Much like wild game caught today.) Even the plant we know of today as broccoli had fewer calories and probably more nutrition. We probably ate piles and piles of plants that had LOADS of vitamins just to get enough calories to live.

To that end we have greatly modified our food supply to be both more delicious, more calorie-dense, but unfortunately less nutrient-dense.

You can look into the now trendy "Paleo-Diet" - which attempts to mimic the diet of our ancestors in order to be more healthy. (Mind you, there's plenty of debate about it's effectiveness.)

Answer 2

There's a 2005 study, and plenty of others, that show a clear dopamine release when sugar is ingested. This one shows that (in rats) it's on par with addictive narcotics.

These results suggest another neurochemical similarity between intermittent bingeing on [sugar] and drugs of abuse: both can repeatedly increase extracellular [dopamine].

This 2013 study shows that high fat foods aren't necassarily more enjoyable so much as removing them from your diet causes physical withdrawl symptoms.

Removal of [high fat diet from people accustomed to it] enhances stress responses and heightens vulnerability for palatable foods by increasing food-motivated behaviour. Lasting changes in dopamine and plasticity-related signals in reward circuitry may promote negative emotional states, overeating and palatable food relapse.

The crummy thing about that one above is that "lasting changes" can be created by poor diet even in childhood.

The cycle of (bad diet in kids) -> (lasting changes in physiology) -> (increased risk of health problems + increased desire for bad diet) is happening to a sickening percentage of humanity at this point.

Anecdotally from my own experience high sugar foods (like candy, or even pie) will give me a splitting headache in minutes. And although I love In-n-Out burgers (w/ fries) there's enough consequence in my mind to keep it from being something I'd want to over-indulge in.