Overeating & obesity: How thousands of years of evolution have hardwired us to abuse food
The data is unambiguous and frightening. We are eating ourselves to death. Literally. Strange way for the wisest, most successful species on the planet to behave, don’t you think?
The world we have created is not the world our bodies and brains expected to inhabit. And we are paying the price. According to the World Health Organization, obesity has tripled since 1975. Over 1.9 billion people are overweight; a third of whom are obese. For the vast majority of human history, starvation and malnutrition were among the greatest threats to our survival. In 2020, overeating is the norm and obesity is the leading preventable cause of death worldwide.
When it comes to the subject of gluttony and obesity, we are quick to pass the blame. Whether it’s greedy corporations, the convenience of addictive, ultra-processed food, misleading advertising, or a lack of healthy options, there is a litany of reasons why our relationship with food is as noxious as ever. And while they are valid reasons, the biggest reason underlying our addiction to food is rarely spoken about.
Put simply, the primary cause of our tendency to overeat is because thousands of years of evolution have trained us to do exactly that. We used to do it to survive, and now we do it because we can. Scientists have labeled this an evolutionary mismatch; a situation where once-useful traits become incredibly harmful when brought into a new, unfamiliar environment.
Before the advent of agriculture around 10,000 years ago, humans lived for hundreds of thousands of years as nomadic hunter-gatherers. During this time, it was far more likely for our ancestors to suffer from being underweight than to suffer from obesity and more likely that they would die of starvation than suffer heart disease or diabetes. Since then, things have changed. Our brains, unfortunately, have not.
Hardwired to binge
The hardwired brain processes that allowed our ancestors to successfully survive and reproduce are the same processes underlying the epidemic of overeating and obesity. For thousands of years, food was significantly more scarce than it is today and every little bit of it required a decent amount of effort to obtain. This was especially true for high calorie, energy-dense foods such as honey or fatty animals. Given our ancestors lived with the ever-looming threat of starvation and the prospect of going days without food, we naturally evolved to value certain foods that could help us survive through periods of famine. Calorie rich/energy-dense foods containing fat, protein, sugar, salt, and starch were extremely valuable as they were rare and meant an enhanced capacity to survive the occasional (but not uncommon) food shortages. When we found these high-calorie foods, it was in our best interest to consume as much as we possibly could. If you didn’t know when your next meal would be, you would probably go for seconds (and thirds) too.
This prompted our brains to associate the consumption of these energy-dense foods with survival and reproduction. When we ate these types of foods we would get a dopamine rush which the brain then (cleverly) used as a reinforcing molecule (encouraging behaviors that led to dopamine releases). This became a major selective force in our evolution, further driving us to seek out and value these foods. Over a long period of time, certain foods became especially rewarding and our cravings for them became deeply ingrained. Now, imagine this same hardwiring in a world where sugary, fatty, high-calorie foods are expertly and insidiously advertised and available on every corner. Junk and fast-food are cheaper, more widespread, more convenient, and more processed than ever before. Deep down we know it isn’t good for us, but our bodies, brains, and instincts still haven’t caught on.
Bang for your buck is nothing new
Turns out that our ancestors loved a ‘great deal’ as much as we do. Given the potential scarcity of food during our foraging days, our ancestors were constantly weighing up the cost of certain foods based on how much time and energy it would take to acquire them. There’s not much point expending 300 calories to obtain 50 calories worth of food (which might be why we don’t have sudden midnight cravings for spinach and other extremely low-calorie foods). Ideally, the higher the calorie return rate, the better. But fast-forward to today, and this makes drive-thru and Uber-eats takeaway pretty hard to resist for your inner hunter-gatherer. An incredibly high-calorie meal that takes almost zero energy to obtain. Jackpot. Given how addictive and unhealthy this type of food is, it’s easy to see how people can slip into overeating and obesity if they aren’t careful and actively resisting their primal urges.
We don’t want to gain weight. Our brains and bodies do.
While we should not shift all the blame to our evolutionary ancestry, the list of reasons why it’s so difficult to limit our intake of food is a lot longer than we think. Since the dawn of humans (and probably well before that), the ability to store body fat has been vital for the survival of our species. Our bodies have developed mechanisms that make it difficult to lose weight as an extra layer of fat can provide us with some much-needed protection from cold temperatures and periods of famine. Our subconscious minds and our bodies have evolved to perceive weight gain as a success.
Evolutionarily speaking, being overweight was better than being underweight in terms of survival. This was especially true in winter when conditions were harsh and food was at its scarcest. If you tend to overindulge in comfort foods during the colder months — you’re not alone. While winter in the modern age poses no greater risk to our health than any other season, we still have a strong subconscious urge to want to load up on fatty, high-calorie foods during winter. This is an especially dangerous habit given how inactive we can be during these months. This brings us to the next point.
So many calories. So few burned.
The modern world has us consuming more and moving less than ever. We might eat as hunter-gatherers would, but we certainly don’t exercise as they did. An important factor that made our ancestors opportunistic binge-eating sustainable was their tendency to live a highly active life. Coming from a context of scarcity, our ancestors had to walk or run for miles to find food. On top of that, most of our food (meat, vegetables, fruits, nuts) took a decent amount of effort just to digest. Nowadays, easy calories that confuse the whole system are everywhere, and most of us live fairly sedentary lives. We stare at a large screen on the weekend, a medium-sized one during the week, and at a tiny one in the spaces in between. We go from couch to car to office chair and the cycle repeats. It’s no surprise we aren’t nearly as lean and mean as our go-getting ancestors.
In 2020, modern humans do not appear to have developed an evolutionary mechanism to help us overcome the lure of sweet, fatty, and unhealthy food. With so much sugar and flavor packed into every bite, resisting the urge to binge-eat these high-calorie foods can be difficult. After all, for thousands of years we have been opportunistically gluttonous anytime we were given the chance. Our ancestors did not practice moderation, and generally speaking, neither do we. There are accounts of the Hadza tribe of Tanzania drinking honey like it was water and eating huge quantities of fatty meat in a single sitting. Sounds like the holidays.
And so, where does all this leave us? Are we doomed to repeat the same self-destructive eating patterns until our heart or arteries finally give out? While the knowledge of our harmfully hardwired instincts to overeat can be discouraging, it reveals one of the central problems of our modern lives. The problem of abundance. There is too much noise, too many choices, too much entertainment, too much information, and too much addictive, unhealthy food. It is the exact opposite problem that our ancestors faced during our many thousands of years of evolution. However, acknowledging our struggle, as new and daunting as it may be, is the first step to understanding the root cause of the problem and making better decisions. Examining our history and how we came to be at this strange moment in history allows us to recognize the biological and cultural challenges of staying healthy in the modern world.
Technological innovation moves at a pace our brains, bodies, and DNA simply cannot. In a very short time, the world has become a vastly different place, leaving our genes in the dust struggling to catch-up. In 2020, we live in a world that our brains and bodies are not biologically equipped to handle. We are extremely susceptible to many of the temptations of the modern world and we are killing ourselves because of it. Understanding and acknowledging our biological instincts is definitely a step in the right direction, but real change, like anything worthwhile, takes real sacrifice. While your biology is yet another factor working against your better judgment, at the end of the day, we choose what we put into our bodies. Let’s hope we begin to choose more wisely in the days, weeks, and years to come. To will power and good health.
My writing is based on true events and stories. It is as real as it gets. I changed parts of the stories and excluded real names as I don’t want people to get hurt. But most of the stuff I write is authentic and includes my thoughts and feelings.