Obesity is a major problem in many parts of the world. In some nations, such as in the U.S. and Mexico, the ratio of overweight to lean people has actually exceeded 1, meaning that there are more overweight individuals than there are lean ones. This is concerning for a number of reasons, one of which is that it’s unhealthy to carry a lot of excess fat mass. When the adipose levels go up, so too does the risk of cardiovascular disease, type-2 diabetes, depression, and many other diseases and health problems. This is not to say that all lean people are healthy (they obviously aren’t) or that everyone whose BMI score has crept past the 25-point mark – the line that officially separates the lean from the overweight & obese – will quickly succumb to a chronic disease; however, in general, it’s safe to say that it’s not a good thing that people’s waistlines have been steadily increasing.
Why are we getting fatter and fatter?
The fact that people are getting fatter and fatter is hard not to notice. Unlike many other health-related epidemics, such as for example those that have to do with mood disorders, gut dysfunction, and food intolerance, the obesity epidemic is clearly visible to the naked eye. All you have to do to see that a lot of people are now either overweight or obese (BMI score >30) is to head out into the streets of a fast food-heavy part of the world – or simply look up a picture of such a place online.
This fact – that a big belly is clearly visible to the naked eye – coupled with the fact that we humans are naturally concerned about our physical appearance, as well as the appearance of others, helps explain why the obesity epidemic has received a lot of attention. It’s regularly featured in the mainstream press; it’s very high on the list of priorities of public health agencies; and it’s a heavily debated topic among nutritionists, doctors, and medical scientists.
The key questions everyone is asking themselves are: What are the causes of the obesity epidemic, and how can we restrain – or perhaps even resolve – the problem?
The vast majority of people recognize that several factors have contributed to driving up the rates of overweight and obesity. With that said, there is no general consensus as to why we’re today in the midst of an obesity epidemic. Whereas some people argue that the primary problem is that we’re taking in too much sugar and refined starch, others say that the no. 1 issue is that we’re spending too much time sitting down. According to them, exercise is the best remedy for obesity. However, others again are opposed to this view, and insist that in the context of overweight and obesity, it doesn’t really matter whether we exercise or not; stating that we’re likely to replace the calories we burn by eating more food.
How is the average Joe to make something meaningful out of this chaos?
I’d argue that the main reason this discussion is riddled with conflict and disharmony is that it’s lacking in Darwinian insights. It’s impossible to fully understand why so many modern humans are obese if one doesn’t know anything about natural selection or the evolutionary history of mankind.
The root causes of the obesity epidemic
Evolutionary science brings harmony, clarity, and coherence to the obesity investigation. Without it, it’s impossible to solve the puzzle that is obesity. To illustrate this, I’ve included a quote from one of the best and most concise papers on this topic that I’ve read to date. The quote, shown below, highlights the core evolutionary reasons why we’re today in the midst of an obesity epidemic…
Three major events in our evolution presaged the current epidemic of obesity and type 2 diabetes. Approximately two million years ago geophysical and climate changes in Eastern Africa triggered dietary adaptations that allowed the growth of our brain. A shift from principally carbohydrate-based to protein- and unsaturated fatty acid-rich food provided sufficient fuel and building blocks to facilitate encephalisation. Insulin resistance may have evolved simultaneously as a means to avert the danger of hypoglycaemia to the brain. Also, thrifty genes maximised food intake and energy storage when available and technical and social progress relieved the selective pressure to maintain an upper level of body weight. Ensuing intellectual capacities enabled two very recent developments that shaped our society of today: the agricultural and industrial revolutions. These socioeconomic landslides changed environmental conditions so quickly that many of us are not yet physically adapted. Reintroduction of carbohydrate as the predominant macronutrient, availability of virtually unlimited stocks of refined foodstuffs and mechanical substitutes of physical efforts render those of us who are genetically designed to survive in harsh circumstances particularly susceptible to obesity and type 2 diabetes mellitus. (1)
The evolution within
The paper I mentioned above provides a great overview of the evolutionary background of the obesity epidemic; however, it doesn’t account for the role non-human biological entities play in shaping our behaviors and nutritional practices. This is arguably an oversight…
Perhaps needless to say, organisms differ with respects to their nutritional requirements, as well as the types of nutrients they can digest and metabolize. This is not just true for animals and plants, but also for microorganisms, including the tiny critters that occupy the human body. This is very important to recognize, in part because it has major implications for our understanding of nutrition, body fat regulation, and obesity.
It’s safe to assume that man-microbe relationships that are mutually beneficial in the context of survival and reproduction have historically been favored by natural selection, seeing as such friendly relationships would be more likely to stand the test of time than unfriendly ones. What’s important to note though, is that we humans have recently changed our environment at an alarming rate. This has dramatically altered the microbial ecosystems we harbor and brought about a major conflict between man and microbes; a conflict that natural selection has never gotten around to resolve, due to the fact that it hasn’t received a strong enough impetus to do so.
The fact that all living organisms are a part of an evolutionary arms race and compete for nutritional resources is very relevant in the context of body fat regulation and appetite control. We can’t just blame the obesity problem on our own genes; we also have to factor into account the fact that we all carry with us a number of smaller organisms, which all operate according to genetic instructions that have been formulated over evolutionary time. Whereas the genetic instructions of some microbes bring about behaviors that benefit both man and microbe, the instructions of others are inimical with respects to the health and fertility of humans. Unfortunately for the modern, doughnut-eating office worker, it’s those latter microbes that flourish in the presence of fast food and pharmaceutical drugs.
The only way to locate the ultimate causes of the obesity epidemic, as well as make sense of what it would take to resolve the obesity problem, is to examine, in a Darwinian way, the evolutionary path that brought us to where we are today. Such an examination reveals that many of the genetically encoded traits that were favored by natural selection because they were advantageous, from a survival and reproduction standpoint, in the past, work against us in the modern environment. It also reveals that the co-evolutionary journey of man and microbes has recently been pervaded by division, turmoil, and conflict, as a result of profound environmental change, something that has contributed to changing our appetite and eating behavior, as well as our health and body fat levels. Last but not least, a Darwinian examination of the obesity problem reveals that we need to adopt diet and lifestyle practices of the past in order to combat the obesity problem we face in the present.