How did we evolve to eat? I’ve been through Paleo Diet two times, and briefly touched on intermittent fasting in the second Paleo refutation. That is how man, no matter where he evolved in the world, ate. We didn’t know when we would get our next meal, therefore, evolutionary mechanisms evolved in us to have intermittent fasting be beneficial to us.
Intermittent fasting is halting the consumption of food for at least 14 hours for women and 16 hours for men. We evolved gathering and eating our food intermittently. Ability to function at a high level, physically and mentally, during extended periods without food, were crucial to human evolution. Your body performs best in a fasted state.
While you’re in a fasted state, the amount of catecholamines (adrenaline and noradrenaline) increase. That is your fight or flight mechanism. Catecholamines also increase fat burning, binding to fat cells putting them out of the cell to be burned off.
With increased catecholamine production from being in a fasted state which burns off body fat, you are also more alert as well. This is another evolutionary advantage. When Man was hunting for food he was in a fasted state, as he didn’t have access to food like we do today. Due to being in a fasted state with increased catecholamine production, this was a great advantage to being better prepared to be ready in case of a surprise attack by a predator or to always be on the ready to attack prey when seen. The scientific literature, though new and growing, supports this thesis with the amount of catecholamine production increased 24 hours after a fast.
Intermittent fasting leads to a dramatic increase in neural autophagy. Autophagy deals with the destruction of cells in the body, controlled digestion of damaged organelles in the cell. The conclusion of the study is, fasting is a simple, easy way to increase neural autophagy. It’s good for keeping the brain healthy, by destroying bad cells, letting the body rejuvenate them.
In conjunction with the evolutionary advantages of intermittent fasting, along with Genetic Similarity Theory, which has those care for others more because they share more alleles in common, and are therefore more closely related, the two evolved hand in hand to better make sure humans survive extended periods of time without food.
Which brings me to ‘starvation mode’. When people bring up starvation mode, they completely misrepresent the Minnesota Starvation Experiment. When they say that metabolic slowdown occurs when food is not consumed for a certain amount of time, they are correct, but they’re only half right. It’s a process called adaptive thermogenesis. Adaptive thermogenesis is the regulated production of heat in response to environmental changes in temperature and diet, which lead to metabolic inefficiency. When they talk about ‘starvation mode’, they talk about not having consumed food within the past, say 2 or 3 hours. That is a completely ignorant statement, as there are no deleterious effects of no food consumption until around 24 hours of fasting. ‘Metabolic slow down’ is not significant enough to prevent weight loss.
Now you may be thinking “What about breakfast, isn’t that the most important meal of the day?” Yes, “breakfast” is the most important meal of the day, but it doesn’t need to be had in the morning, immediately upon waking. The average person sleeps for about 8 hours, during that time, the body enters the fasted state. The “breakfast is the most important meal of the day myth” was originally pushed by Kellog’s in the 50s. The problem with any of these studies in regards to weight loss and or any other conclusions is that they are observational studies. The actual cause cannot be quantified. The slogan was created to obviously give Kellog’s more business, which was based on observational studies. The main hormone behind post-breakfast hunger is cortisol. The term ‘breakfast’ means “break your fast”, therefor “breakfast” can be had anytime AFTER your body goes into the fasted state.
Cortisol is secreted in response to a stressor, in order to help you cope with that stressor efficiently. Exercise (hunting for our ancestors), disrupts homeostasis because of the stressors that are put on the body. The stressors then require an adaptive response, which is cortisol. Most anything our ancestors did disrupted homeostasis, causing cortisol to be secreted. Because of increased cortisol levels during times of need, you can push through certain things than if you didn’t have that cortisol increase due to the stressor that made your body secrete the extra cortisol.
The stressors that our ancestors had to survive in the past, though, had a clear-cut line in beginning and end. Therefore, the fight or flight mechanism (catecholamine production) was easily secreted to elicit the needed response in order to survive, get food, and ultimately what evolution is about, making sure your shared genes pass on to the next generation. All of these responses in regards to intermittent fasting increase Man’s success on the planet, as well as evolutionary fitness. The strong selection pressures then select for those traits which are more advantageous, which pass down through the generations, getting better or becoming obsolete through non-use, e.g. migrating to a new area where those selection pressures that had certain traits arise weren’t in the new area.
To talk about another hormone, there is a hormone called ghrelin, which is secreted by the stomach in anticipation for a meal. It decreases after meal consumption and also stimulates the release of the growth hormone.
An evolutionary advantage for ghrelin is that it let Man know when the last time he ate was, as our bodies are pretty much like clocks and tell us certain things when it needs them, e.g. releasing ghrelin when it needs nutrients and sustenance, so they can then go and hunt for food, ensuring that their genetic lineage survives.
The drive for food, the drive to make sure genes pass on to the next generation, intermittent fasting and evolution of man, all intertwine with each other to tell the story of how we got to where we are today. There are way more health benefits to restricting periods of being in a fed state, and the evolution of those adaptive processes in our bodies from thousands of years of eating intermittently which our bodies had to evolve the traits that had us succeed in order to pass our genes on to the next generation. Everything we do in life is, at the most basic level, driven by our biology and the release of certain chemicals/hormones that make us seek out or want certain things.
In summary, the release of catecholamines in response to lack of food after a certain amount of time is one such example that shows that those evolutionary processes evolved to better protect us from extended periods of time without food, as well as giving us great benefits due to how our bodies evolved in response to those adaptations. This also leads to increased altruism for those with close genetic similarity, e.g. more alleles in common than with other peoples. The increased catecholamine production leads one to be more alert of their surroundings, which is an evolutionary advantage due to the release of ghrelin making man hungry, which in turn led to searching for food. That then led to an increase in the catecholamines to increase those adrenaline hormones to make man better prepared for any attack by a predator, and to be ready for any perspective prey he saw. Intermittent fasting, including all hormonal advantages involved with it, evolved closely together with altruism for one’s own people. This led to an increase in genetic fitness, as well as having a better chance to pass your genes on to the next generation.