The Paleo Diet has skyrocketed in popularity over the last several years, and millions of people worldwide now swear by a hunter-gatherer type diet to lose weight, build muscle, and increase longevity. However, not everyone is so enthusiastic about the prospect of eating like our prehistoric ancestors. As with most things that are “new” and unorthodox, the Paleo Diet has been subject to much debate and controversy. On the one side you have those of us who follow a paleo-based diet and praise the benefits of looking back at our evolutionary past to understand how to eat, while on the other end of the spectrum there are those who claim its just another “fad diet”. I’ve written a lot about the research on the Paleo Diet before, and in this post I want to summarize the top four reasons I believe a paleolithic, hunter-gatherer type diet is the eating strategy to choose for those that are looking for optimal health. Not in a strict, never eat dairy and dark chocolate kind of way, but definitely as the basis for healthy eating.
1. Millions of years of human evolution shaped our dietary needs
When researching the connection between nutrition and health, many would say that the first step is to go for the randomized controlled-trials, meta-analyses, and systematic reviews on the subject you’re interested in. After all, these types of studies are considered the gold standard of nutritional science. I agree that RCTs and comprehensive reviews are absolutely invaluable when digging into nutrition and health topics, but the problem I see with initiating the search for answers this way is it can often lead us astray.
I think one of the primary reasons there’s so much confusion and debate about nutrition is that there are a thousand different ways to look at the science/literature. Someone who’s drawn to the vegetarian movement will quickly focus on the studies that seem to support his cause, while those who favor a very low carb diet will point out the dozens of trials that seemingly support their ideas.
Even someone with no apparent preconceived notions can quickly be led astray and come to the wrong conclusions by looking at the research. Let’s take a subject like saturated fat for example. On the one side, there are plenty of seemingly good studies showing that a diet high in saturated fat can trigger low-grade chronic inflammation, while on the flip side there are also several reports indicating that saturated fat consumption is not linked with higher risk of atherosclerosis, heart disease, and all the other conditions butter and lard have been blamed for. The reason for these conflicting results often boil down to differences in study design and methods, and it can often be difficult to seperate what is good and bad data. Without a guiding framework to help us make sense of things, we’re grasping in the dark.
So, what is this guide we need to make sense of nutritional science? Evolution, of course!
By looking at how we’ve eaten for millions of years, how our brains and guts have evolved, and how nutrition transitions have impacted human health, we establish the foundation we need to design a healthy diet in the 21st century. It’s not always easy to decipher our evolutionary history in such a way that we can draw concrete conclusions, but even by just getting a fraction of the answers we are looking for, we can begin to make sense of why things are like they are. With this evolutionary perspective in mind, we suddenly have a base to build our ideas upon.
Darwin didn’t focus much on nutrition and exercise, but he unknowingly gave us many of the tools we need to be healthy and fit in his book “On the Origins of Species”. By combining his ideas on evolution and natural selection with the science on epigenetics and microbiomes, it’s usually possible to predict what nutrition studies will show even before they have been done. That doesn’t mean doing and reading research is a waste of time – of course not. But what I’ve come to learn is that having a basic understanding of evolutionary biology is far more powerful than any RCT or comprehensive review will ever be.
Over millions of years of living as hunter and/or gatherers, natural selection shaped the genome that we to a large extent still carry with us today. The data consistently show that we are still very much stone agers from a genetic perspective (1, 2). The dietary changes that began with the agricultural revolution – and even more so with the industrial revolution – are extremely recent on an evolutionary time scale. 10.000 years is just a blink of an eye from an evolutionary perspective.
Certain genetic changes, such as increased frequency of lactase persistent alleles and alterations of the gut microbiome, have allowed us to tolerate more “neolithic foods”; but we are clearly not well-adapted to the grain-based, starchy diet most people consume today. Healthy, non-modernized populations often prepared/processed grains and dairy in such a way that the end product was lower in carbohydrates and antinutrients, but sadly we’ve now abandoned many of these techniques. Traditional processing methods such as soaking and fermentation should be employed if grains and dairy contribute a large part of the diet, but even then we’re probably best off eating these foods in moderation.
2. Populations eating paleolithic, hunter-gatherer type diets are extremely healthy
When looking into the health effects of the Paleo Diet, I think a good way to start is to look at the people who actually eat this type of diet. As everyone who’s been reading this blog for some time knows; hunter-gatherers and other non-westernized cultures eating ancestral diets tend to be extremely healthy. Their average lifespan isn’t that long, but that’s not due to high cancer rates and cardiovascular diseases, but rather because of little access to modern medicine (3). In the industrialized world, public health advancements and medicine have given us the opportunity to profoundly decrease infant mortality and prolong the lives of old and sick people. We live longer, but we aren’t healthy.
Also, the fact is that when we look at the life expectancy of an adult hunter-gatherer, the stereotypical image of nasty, brutish, and short lives doesn’t reflect reality. Studies of several hunter-gatherer societies suggest that modal age of adult death is about seven decades (adaptive life span of 68-78 years), and contrary to most westerners, these people tend to be healthy all the way up to old age (4).
How long can we live if we adopt the best from both a hunter-gatherer existence and the modern world?
When we take evolutionary mechanisms into the equation, it makes sense that these non-westernized populations don’t suffer from the types of mismatch diseases we see in the modern world. For millions of years, a hunter-gatherer way of life dominated our existence, and in this ancestral environment, those who were not fit enough to hunt and/or gather for food and evade dangerous animals were quickly weeded out of the gene pool. In contrast to the modern environment we’ve now created for ourselves, reproductive fitness was tightly linked with physical fitness. This is how it is for all wild animals who struggle for their existence. To be able to survive and reproduce, you have to be fit enough to handle a demanding lifestyle.
Through natural selection we evolved our distinct digestive system, muscles, and brain. We became adapted to a hunter-gatherer way of life. So, when we understand how natural selection drove the evolution of our species, the low rates of “non-communicable” diseases in hunter-gatherer populations doesn’t come as a surprise, as they live in a type of environment that resembles that which we are best “genetically adapted” for.
For male hunter-gatherers, it makes sense that those where physically fit and strong up until old age would have a higher reproductive fitness than those less physically fit – and they would therefore pass on more of their “good genes”. For female hunter-gatherers, the story is perhaps a bit more complex. Evolution only “cares” about health as long as it impacts survival and reproduction. Why do women survive so long past menopause? The grandmother hypothesis might explain this phenomenon by suggesting that being long-lived provided an advantage as it allowed for women to take care of their children and grandchildren.
Anyways, let’s return to the Paleo Diet. As noted, studies consistently show that non-westernized populations eating paleolithic diets are virtually free from cancer, heart disease, acne, inflammatory bowel disease, and several other disorders that are now becoming increasingly common in the modern world (2, 5).
But as any scientist would point out: Despite the consistent nature of these studies, they are largely observational. They don’t prove a causal relationship between diet and health, as there are certainly many other factors beside diet that contribute to the good health of hunter-gatherers. So, let’s take a look at intervention studies to see what happens when overweight westerners give the Paleo Diet a try.
3. Intervention studies show that a Paleo Diet is superior to other “healthy” diets
An evolutionary perspective and data on hunter-gatherers provide a good foundation, but to really establish cause and effect, we need to dig into the intervention studies done on the Paleo Diet. Sadly, there are “only” about a dozen of these studies looking into the effects of a paleolithic diet on fat loss, insulin sensitivity, and/or other markers of health. It’s very difficult to get funding for these types of trials, especially since a Paleo Diet goes against most of what the official dietary guidelines in most countries tell us to eat.
Studies where westerners are put on a paleo-type diet consistently show that this type of dietary pattern has a potent effect on fat loss, insulin sensitivity, and several other markers of health (6, 7, 8, 9, 10, 11, 12, 13, 14). The problem isn’t that the results from these studies aren’t convincing, it’s that at the moment the studies are too few and too small to make an “impression” on the conventional nutritional community. Research funds allocated to Paleo Diet studies are just a drop in the pond.
Swedish scientists have been pioneers in this field. Hopefully more will follow…
Let’s do a run-down of the 4 randomized-controlled trials that have tested the Paleo Diet against other healthy diets:
- In a randomized cross-over study, 13 patients with type 2 diabetes, 3 women and 10 men, were instructed to eat a Paleolithic diet based on lean meat, fish, fruits, vegetables, root vegetables, eggs and nuts; and a Diabetes diet designed in accordance with dietary guidelines during two consecutive 3-month periods. Over a 3-month study period, a Paleolithic diet improved glycemic control and several cardiovascular risk factors compared to a Diabetes diet in patients with type 2 diabetes (11).
- Twenty-nine male IHD patients with impaired glucose tolerance or diabetes type 2, and waist circumference > 94 cm, were randomized to ad libitum consumption of a Paleolithic diet (n = 14) based on lean meat, fish, fruit, vegetables, root vegetables, eggs, and nuts, or a Mediterranean-like diet (n = 15) based on whole grains, low-fat dairy products, vegetables, fruit, fish, and oils and margarines during 12 weeks. A Paleolithic diet is more satiating per calorie than a Mediterranean-like diet (12).
- Twenty-nine patients with ischaemic heart disease plus either glucose intolerance or type 2 diabetes were randomised to receive (1) a Palaeolithic (‘Old Stone Age’) diet (n = 14), based on lean meat, fish, fruits, vegetables, root vegetables, eggs and nuts; or (2) a Consensus (Mediterranean-like) diet (n = 15), based on whole grains, low-fat dairy products, vegetables, fruits, fish, oils and margarines. A Palaeolithic diet may improve glucose tolerance independently of decreased waist circumference (13).
- Seventy obese postmenopausal women (mean age 60 years, body mass index 33 kg/m2) were assigned to an ad libitum PD or NNR diet in a 2-year randomized controlled trial. A PD has greater beneficial effects vs an NNR diet regarding fat mass, abdominal obesity and triglyceride levels in obese postmenopausal women; effects not sustained for anthropometric measurements at 24 months (14).
4. A properly designed Paleo Diet has all of the characteristics of a diet that makes you healthy and lean
With a basic understanding of human nutrition, you don’t even have to look at the studies to understand that the Paleo Diet will be a great choice for people who want to improve their health and/or lose weight.
- A “typical” Paleo Diet is high in protein and fiber and relatively low in carbohydrate.
- The Paleo Diet is devoid of trans fatty acids and refined sugars.
- All of the plant foods (fruits, vegetables, etc.) allowed on the Paleo Diet have a maximum carbohydrate concentration of approximately 23% (5).
- The Paleo Diet is extremely nutrient-dense (15).
- All of the foods allowed on the Paleo Diet have a low-moderate reward value, low-moderate energy density (honey and very fatty meats being the exception), and high satiety index (they fill you up).
When we combine all of these things, we get a diet that has all of the characteristics that science tells us make you fit and healthy. After all, these are the types of foods we’ve been consuming for millions of years, so there’s not really a surprise that we’re well adapted to eat them.
If there’s one thing the evolutionary perspective on human nutrition teaches us, it’s that most of the food groups that have been introduced since the agricultural revolution come with some potential downsides; at least when they are not prepared using traditional processing techniques. Grains are extremely high in carbohydrate compared to ancestral foods and often come with a hefty dose of antinutrients. Dairy milk is full of hormones and bio-active peptides that are actually meant to boost the growth of calves. Butter, GHEE and oils are extremely calorie-dense compared to anything we’ve been eating throughout most of our evolutionary history. And as for more novel things we eat today, such as pizza, pastries, and all the other products we’ve designed for ourselves, widespread consumption can only lead to one thing: Overweight, obesity and metabolic havoc. These types of foods have a nutrient composition that doesn’t resemble anything found in nature.
As always, all of this doesn’t mean that you have to ditch all of the cheese, butter, wine, and dark chocolate from you diet and stick to a strict Paleo Diet. However, in my mind there’s no doubt that primarily eating from the food groups that have been with us throughout most of our evolutionary history is the best way to go.