Addiction is a strong word, and not entirely accurate when it comes to foods, but there are substantial effects on the brain from food. (And, it is possible that if an individual experiences prolonged stress, anxiety, depressed mood and boredom, a genetic or acquired propensity to overeat may be activated and cause addiction-like eating behavior.)
The food you eat can change your brain.
Assuming we’re properly nourished, our bodies have feedback loops in place to tell us when we’ve have enough to eat (we learned about this in the lesson on Head Hunger). But these balanced loops can become disrupted — quickly — when we eat certain types of food. A diet filled with hyper-palatable, hyper-rewarding, heavily processed foods can overthrow the brain’s “stop” signals.
“Junk foods” that are sweet, salty, creamy, and/or crunchy (maybe all at once), and full of chemical goodness spin our pleasure dials… but contain relatively few actual nutrients. We end up feeling less satisfied from the lack of nutrients and want to eat more. And our bodies even fight to hold on to the weight we gain.
Hyper-palatability, aka tasty
Palatability is more than just taste — it’s our whole experience of pleasure from a food. That includes taste as well as aroma, mouthfeel, texture, and the whole experience of eating. Palatability strongly influences how much we eat at meals. That seems obvious: Of course we eat more of the foods we like. And of course some foods are more pleasurable to eat than others.
But some foods aren’t just palatable — they’re extremely palatable. They’re what you might call “too good”. Anything that you “just can’t stop eating” would fall into this category.
Why we love these foods
We have evolved to love foods with high fat content, high refined starch and/or sugar content, saltiness, and sweetness. Our ancestors didn’t have food readily available, and they had to work hard to get it. Our brains learned that high-fat foods are energy dense, a sweet taste can tell us a food is safe to eat, and bitter-tasting foods could be poisonous.
The more of those elements in the food, the more we want it
Make something salty, and sweet, and starchy, and fatty, then add in some extra flavors and scents, appealing colors and a pleasing mouthfeel for good measure, and you have something that’s been scientifically engineered for us to over-eat. If you love “junk food”, and feel like you can’t stop eating it, you’re not alone, bad, or weird. You are just being manipulated by the food companies …
This magical mix is rarely found in nature. It is, however, often found in highly processed foods like cakes, cookies, pastries, pies, pizza, ice cream, fried foods, and so forth. And the high-fat foods we crave aren’t nutrient-rich animal organs or blubber that we had to work nine hours to get; they’re Frappucinos and bacon double cheeseburgers that we bought while seated in our car. So now, evolution’s gifts now work against us.
Reward value, aka fun
Along with palatability, some foods give us a “hit” or a reward. This rewarding feeling of pleasure results from complex brain signaling processes, which are generated upon seeing, smelling, and tasting food. The food texture can also generate pleasure via specific sensors located in the mouth. These brain signaling processes are very similar to those involved in drug addiction (although not to the same degree).
We’ll go out of our way to get foods with a high reward value — in fact, we may learn to like them even if they don’t taste very good, for example coffee or beer.
Few people like black coffee or beer the first time they try them, but coffee has caffeine (yeah!) and beer has alcohol (double yeah!) and because our brains like caffeine and alcohol, we learn quickly that coffee and beer are good things, and we learn to like (or at least tolerate) their taste. Over time we discover we like — maybe even can’t live without — them. We’ll wade through a crowded bar to buy a drink, we’ll stand in an absurdly long line for our afternoon coffee fix, and we’ll pay exorbitant amounts of money for relatively simple products. (And the food companies love this!! Cha-ching!)
We’ll also make room for high-reward foods even when we’re full.
Tasty + fun = no shutoff switch
Now, what happens when you put these two things — hyper-palatability (tasty) and high reward (fun) — together? A dangerous combination. We want these foods, we like these foods, and we’ll work hard to get them. When we do get them, we often don’t quit eating them.
But, of course, these processed foods that our brain looooooves are horrible for our bodies. These semi-addictive foods aren’t usually very nutritious. They have more energy (calories) than we need, with fewer nutrients (i.e. vitamins, minerals, phytonutrients, essential fatty acids, etc.) and fiber. We don’t feel full or satisfied when we eat them.
After a while, our brain forgets about its natural “stop” signals in favor of getting more of that delicious “hit” from food reward. Our Head Hunger pleasure system starts bullying our Belly Hunger homeostatic energy-balancing system.
Over time, if we eat a lot of these foods consistently, we might even injure and inflame the parts of our brain that regulate our food intake and energy output. Now our homeostatic regulation isn’t just getting pushed around, it’s also on fire.
Food coma, or, “Junk Food Makes You Stupid”
We’ll learn more about gut bacteria (your microbiome) soon, but a quick summary is that the bacteria in your digestive system has a surprisingly large influence on neurotransmitters and your brain. A high-sugar, high-fat diet causes changes in gut bacteria that seem to lead to significant losses in cognitive flexibility, a measurement of the brain’s ability to switch between thinking about one concept to another, and to adapt to changes in the environment. A high-sugar diet was particularly detrimental to brain function, leading not only to decreased cognitive flexibility but also to impairments in short- and long-term memory.
In addition, getting too much energy from foods, and especially junk foods, seems to injure our brain’s neurons, particularly in the hypothalamus. When injury occurs in the body, our bodies release inflammatory cytokines (aka cell signals), which in this case causes hypothalamic inflammation, and this hypothalamic inflammation disrupts the hunger feedback loops.
Now, as a result of eating the tasty food that our bodies have evolved to crave, we have a disrupted hunger feedback loop, along with decreased brain function, so we have a harder time stopping the cravings and figuring out a more nutritious way to eat … it sounds hopeless! What do we do? Take it one step at a time. One habit at a time.