Intermittent Fasting (IF), a nutritional strategy that involves fasting for intermittent periods of time, is all the rage these days. Over the past decade, more and more people have jumped on the IF bandwagon, and an ever-growing number of websites, books, and articles devoted to this time-restricted way of eating has appeared. IF has certainly sparked a lot of debate. While some people are highly skeptical to this nutritional strategy and cling to the old dogma saying that it’s important to eat every 2-3 hours throughout the day in order to keep blood sugar levels stable, others are highly enthusiastic about IF. Some even go as far as to say that IF transformed their lives.
The public perception seems to be that IF is something new – a way of eating that has only become common quite recently. This isn’t surprising, given that we – as a society – have been told for decades that breakfast is the most important meal of the day and that it’s better to eat many small meals every day than a couple of large ones. It’s only quite recently that people started to challenge this dogma and the IF movement gained traction. What is often forgotten though, is that the practice of fasting stretches much farther back than living memory. The fact that it’s only quite recently that IF has gained mainstream attention doesn’t mean that IF represents a new way of eating for humans. It doesn’t…
Our bodies expect to go hungry every now and then
The weight of the evidence suggests that modern hunter-gatherers rarely experience long periods of food shortage (famine) (1). That said, they obviously don’t have endless, easy access to food. IF is naturally incorporated into their eating schedule (2), in part because they have to hunt and gather for the food they eat. Typically, these food-acquiring activities take place early in the day, which means that eating may not occur until long after dawn.
Intermittent periods of fasting were undoubtedly a natural part of the lives of ancient hunter-gatherers as well. They obviously didn’t plan that they were going to abstain from eating for 16 or 18 hours every day, but rather fasting occurred naturally as a result of fluctuations in food availability, season, and climate. Some days, they may have taken in food many times during the day at different time points, whereas other days they may have eaten only one meal – or perhaps no food at all.
This is how it is to live in a natural environment. You don’t have constant access to food. You don’t always know when or what your next meal will be. You have to adjust to your circumstances, which can change rapidly.
The health benefits of fasting
I would argue that we’re genetically adapted for an eating pattern that has periods of fasting incorporated into it. We should go hungry every now and then. Eating all the time, never giving our digestive machinery a rest, is not wise. This notion is supported by the evolutionary evidence, as well as a growing body of research linking IF with various health benefits, including fat loss, improved glycemic control, and reductions in blood pressure (3, 4, 5, 6).
With all of that being said, IF is no panacea. It’s not going to cure your autoimmune disease, make you lose 10 pounds in a week, or give you rock-hard abs. At least not by itself. It has to be combined with a healthy diet, good sleep, exercise, and so forth. IF is not the foundation of the cake, it’s merely the icing on the top.
Moreover, it should be noted that most of the scientific evidence pertaining to the health benefits of fasting is derived from studies with male participants. There’s a paucity of data on IF in relation to women’s health. It’s possible that the health benefits of IF are more powerful in men than in women, but more studies are needed to make firm conclusions.
Finally, it’s important to point out that we humans can adjust to a wide variety of different eating patterns – some healthier than others. While some indigenous, ancestral people have been known to consume many small meals every day, others eat fewer, larger ones. Often, the meal schedule changes from day to day and also from season to season. What many of these people have in common though is that they fast every now and then – sometimes for a whole day or more if they don’t manage to get a hold of food.
As a whole, I would say that the evidence clearly indicates that the notion that we humans do best on a set meal schedule that consists of many small meals every day is fallacious. It’s not necessarily anything wrong with eating many small meals throughout the day – some people, in particular hard-training athletes, typically do well on such a schedule, due to the fact that they need to eat a lot of food to fuel their athletic activities – but it’s not necessary, or even ideal, in most cases.
When IF causes problems
Not everyone does well on an IF protocol. Some people report that they get cravings for sugar, feel they can’t function mentally, and/or get a nagging headaches. In some instances, these problems can be attributed to the novelty of IF. If you’ve eaten breakfast early in the morning every day for your whole life, it will take some time before you adjust to an IF-type meal schedule. Another common cause of these problems has to do with diet quality and health status.
Something that seems to elude a lot of people is that there are biological systems in place in our bodies that help us appropriately regulate food intake. Instead of setting up a strict meal schedule and timing and planning our every meal, we’re probably much better off just listening to our body – eating when we’re hungry and drinking when we’re thirsty. There’s one caveat to this principle though, and that is that a lot of contemporary humans are so damaged on the inside – their microbiota is perturbed, their bodies are inflamed, and the machinery involved in regulating appetite is impaired – that they take in too much food, too often. These individuals have to take steps to resolve this problem before they can attain a normal, healthy appetite.
Part of the reason so many people today go around feeling hungry all the time and crave highly processed food is that they adhere to an imprudent diet. Paleo man ate a diet that was fairly low in carbohydrate and high in protein, fiber, and omega-3: a very different diet from the modern, western one. His body was accustomed to function well even when it hadn’t been fed for many hours, which is not the case for the body of the modern man – which is used to a steady supply of easily digestible carbohydrates.
A healthy body coupled with a healthy diet does much better on an IF-type eating plan than an unhealthy body matched with an unhealthy diet. How you feel on an IF-type meal schedule and the results you see from adhering to this type of time restricted feeding plan largely depend on what you eat and how healthy you are. In other words, skipping breakfast, by itself, is not going to lean out your body and give you a healthy, muscular physique, you also have to dial down your diet and make sure your body is operating at a high level.
IF is by many considered to be a fairly new nutritional concept, which isn’t surprising given that it’s only quite recently that IF has gained widespread attention within the world of health/nutrition/fitness. In reality though, IF is nothing new – it’s an ancient way of eating. Unlike us, our ancient ancestors didn’t have easy access to food at all times. They had to put in work to get a hold of something to fill their bellies with and obviously didn’t adhere to a set meal schedule. Some days, they may have eaten many small portions of food throughout the day, whereas other days they may not have eaten at all. Fasting is a natural part of the original human meal pattern. Going hungry every now and then is both healthy and evolutionarily normal.
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