Updated: Mar 15
I always like to think about things from an evolutionary perspective. If we think back to what life would have been like between 6 million years ago (when the last common ancestor between humans and apes lived) and now, there were probably times where our ancestors were forced to fast. It wasn’t an intentional act it was just the way of life then when food wasn’t as readily available, and our ancestors had to work hard to get it.
This is especially true when it comes to Neanderthals and the first modern humans that first evolved around 250,000 years ago. There is evidence that these particular ancestors of ours were high level carnivores, eating a diet almost entirely made up of animals. (1,2) At this time, humans and pre-humans were very prolific hunters, but finding, hunting, and killing the next meal takes a lot of time and there could have been times when food was few and far between. This would have been especially true in winter.
In summer, if hunting was unsuccessful, some plant foods probably were eaten at times which would have prevented starvation and likely resulted in less fasting. However, in winter, those foods would not have been available (because plants are seasonal) and fasting for extended periods was probably a reality. On a weekly basis, there were probably ebbs and flows of feasts and famine. Since this was the way of life for a very long time during our ancestors slow evolution to becoming human (from about 2.5 million years ago until about 10,000 years ago), it is safe to assume that evolutionary adaptations to fasting would have become engrained into our physiology. On the flip side, it is no wonder that humans experienced health issues (metabolic syndrome) when eating became a frequent event throughout the day.
Eating all multiple times a day started during the Agricultural revolution, this happened about 10-12 thousand years ago and is the first time we seem humans staying in one place and farming crops. Farming provided an abundance of calories, though they were nutritionally poor and lower quality calories compared to the animal food calories that literally made us humans what we are. Yet, these abundant nutrient poor calories did the job of allowing us to reproduce and grow in numbers very quickly. While the population did grow, there is lots of evidence that the health of humans suffered during this time. (3)
I believe the poor health that those first farmers had was in part due to eating a lesser quality food (crops), but was also due to over consumption of these foods. Since these foods were less nutrient dense, and less bioavailable to our bodies, we ended up having to eat a lot more calories in order to get the nutrients we needed. This was the beginning of what became the constantly eating society we have today.
However, throughout the history of civilization, different societies found the value in not consuming food constantly. Historians say that the Romans were known not to eat breakfast because it was thought to be healthier. Eating more than one meal a day was sometimes said to be a form of gluttony. Even in the middle ages fasting was very common, especially among monks who tried to set an example for people of that time.
If we fast forward to today, we have a society where huge quantities of food are available to us all day every day (especially in westernized countries). This is largely the result of the food industry. In the early 1900’s John Harvey Kellogg invented the first breakfast cereal and a big push for breakfast was put forth by the industry. By the 1920’s and 30’s the government was promoting a breakfast of processed grains and sugars as the most important meal of the day.
Interestingly, this was also when we started to see major changes in human health like increases in obesity and heart disease. There were many changes during this time like the introduction of seed oils and increased toxin exposure, but breakfast becoming a way of life for people only increased their consumption of empty calories and very likely contributed as well.
So, our physiology was shaped over millions of years in a time when calories were not always available and fasting was a way of life. Then we went to eating constantly in a relatively short amount of time, this helps explain our increase in metabolic chronic disease as we have overtaxed our metabolism since the introduction of these plentiful empty calories. Following this logic, it would make sense that returning to a restrictive eating regimen would help us achieve health by putting our physiology back in an environment it I smore evolved to. Let’s see what the research says.
First off, there is some pretty compelling research showing that restricting calories through intermittent fasting or a ketogenic diet is very good for lifespan and health span. One study, done in mice, found that “energy-controlled high-fat LCD’s are not detrimental to health, but rather a KD extends lifespan and slows age-related decline in physiologic function in mice”. (4) That is a pretty enticing finding for anyone wanting to live a long and fulfilled life. Cut the carbs and empty calories and go with the more satiated nutrient dense fats.
I believe this longevity effect has to do with the autophagy (cleaning up of old cells to make room for new ones) that is induced by fasting. For one, autophagy induced through fasting has been shown to have benefits to the heart. (5) One study stated that “the preponderance of evidence suggests that autophagy and mitophagy are important protective mechanisms across the spectrum of ischemic injury”. (6) But it could be other longevity effects as well, as fasting has been shown to help us maintain muscle mass (7), which is the best indicator of health as we age. (8)
Another study found some very interesting changes in physiology when people fasted. When researchers had a group of people fast for 1-week they saw that their total cholesterol, LDL, and Apo-B levels all go up substantially. LDL went from an average of 114 to 190 (see graph below), that’s a 40% increase. (9) This is likely because the process of making ketones (which the body has to make for a fuel source during fasting) is the same pathway for making cholesterol. So, cholesterol goes up by default.
If you follow my blog, you know that I have discussed how cholesterol does not cause heart disease. But this phenomenon of cholesterol and LDL going up shows why those molecules don’t cause heart disease from yet another angle because fasting also has major benefits to the heart. In one study, researchers fed one group of rats on an intermittent fasting schedule and another group more frequently. They then induced heart attacks in all the rats. The group who had been fed on an intermittent fasting schedule had much smaller heart attacks, much lower amounts of apoptosis (programmed cell death of heart tissue), and much lower inflammation overall. (10) You can see this in the graphs below.
Other studies have shown and given explanations for the cardioprotective effects of fasting. (11) One study showed that in people who had been intermittent fasting for anywhere from 3 to 15 years they had much better levels of what the researchers called “markers of atherosclerosis”, though they wrongfully included cholesterol and LDL in that list. (12)
They also found that those individuals who practiced intermittent fasting had about 40% less atherosclerosis in their carotid arteries than the control group. When the research defined atherosclerosis as “more than 1 mm” of increase thickness of the carotid artery, this meant that the 40% decreased amount of atherosclerosis in the intermittent fasting group actually meant that none of them had any atherosclerosis.
Stringing some of this research together, I want to point out that if fasting has been shown to cause an increase in cholesterol yet also reduce the size of induced heart attacks, reduce cell death during heart attacks, decrease levels of inflammation, and significantly reduce development of atherosclerosis, then how could cholesterol be the cause of heart disease? Just more evidence of how misled we have been when it comes to the cause of our heart disease epidemic.
I highly recommend practicing fasting. You can do this in various ways. I like to eat two meals a day within a 6 to 8-hour window. Also, about 3 times a year I do a longer fast of about 2-3 days. Implementing these strategies brings us closer to living in a way more compatible to our evolved physiology and can give us huge health benefits, especially for out heart.
Stay healthy out there!
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