There are few topics in nutrition that have been subject to as much debate as the intake of protein, fat, and carbohydrate. On one end of the spectrum, there are the proponents of plant-based diets, including many vegans and vegetarians, who advocate a high-carb, low-protein, and low-fat diet, while on the other end, there are those who favor a diet that is very high in fat, moderate-high in protein, and low in carbohydrate.
For the Average Joe with little to no knowledge about nutrition – and even for those with a deeper understanding – all of the conflicting advice on macronutrient ratios and carbohydrate intake that’s being pumped out from blogs, health authorities, and newspapers can make it difficult to know what to believe. For some, the macronutrient ratio and composition of the diet end up being determined by fluctuations in dietary trends, with a low-carb diet for a couple of months, a plant-based template for a period, and then a juice fast for a week or two…
A controversial topic
Why is there so much controversy surrounding the intake of protein, carbohydrate, and fat? One of the most obvious answers to this question is that humans can thrive on a wide variety of different diets. While many animals on this planet have a relatively narrow/constrained species specific diet, humans can be healthy and fit on diets with widely different macronutrient compositions.
The Okinawans in Japan, who are known for being among the most long-lived people on earth, and the Kitavans on the island of Kitava, with their superb health markers, are two examples of traditional people who seem to maintain very good health on a high-carbohydrate, low-protein diet. On the flip side, you don’t have to look far and wide to find healthy traditional populations – such as the Inuit and the Maasai – who eat a diet that is high in fat and moderate-high in protein. This clearly doesn’t mean that all of these diets are equally healthy or that the macronutrient ratio doesn’t matter, but it does highlight one of the reasons why there is so much controversy surrounding how much protein, fat, and carbohydrate we should eat.
Another reason why macronutrient intake is such a controversial topic is that a lot of dietary advice isn’t rooted in an evolutionary understanding of human nutrition. Let’s take public dietary guidelines for example. For decades, the idea that we should all eat a grain-based, low-fat diet has been ingrained in the public’s mind through food pyramids, public health campaigns, and commercials for fat-reduced food. This has led many people to think that this type of diet is the “natural” human diet. From an evolutionary perspective, this notion makes little sense…
Through the lens of evolution
If we expand our perspective beyond the modern age and into our evolutionary past, it quickly becomes clear that we miss out on huge chunks of the nutritional puzzle if we only focus on what’s been going on in the world of nutrition for the last century or so. For 99.5% of the evolutionary history of our genus, Homo, we lived as hunter-gatherers, and during this time, most of the foods that now make up the typical Western diet, such as grains, refined vegetable oils, and dairy, were not routinely eaten by any humans.
All of this doesn’t mean that we should necessarily avoid all of the foods that came into the human diet after the Agricultural Revolution; it just means that we should flip our focus. Instead of using the Modern Age as our starting point for looking at human nutrition, we might want to turn the clock back, start at “the beginning”, and study the evolutionary dietary road that led us to where we are today.
So, you might ask, how far back should we go? To really get a grasp of how our bodies evolved and what types of foods we’re best adapted to eat, we have to go back and look at all of the known stages in our evolutionary journey. That said, from the perspective of diet, it’s clearly the Paleolithic era and the diets consumed by members of our genus (in particular Homo sapiens sapiens) that are most important to keep in mind.
Although proponents of plant-based diets will often tell you otherwise, there’s no doubt that animal source food was an important part of the diet of our Paleolithic ancestors (1). Several lines of evidence show that animal source foods started becoming an increasingly important part of the hominin diet starting about 2.5 million years ago; a dietary shift that set the stage for the rapid growth of the large, complex brain of Homo erectus and other species that belong to the genus Homo (2, 3, 4).
In a paper from 2006, Boyd Eaton suggests that behaviourally-modern humans in East Africa 100-50 x 10(3) years ago obtained about 35% of their dietary energy from fats, 35% from carbohydrates, and 30% from protein, which is a very different macronutrient breakdown than what is considered “normal” today (5).
Following our species’ migration out of Africa approximately 70.000 years ago, humans started to settle down in different habitats around the world, something that resulted in the adoption of new and different dietary patterns. Hunter-gatherers who ventured into northern areas of the world (tundra and northern coniferous forests) typically ended up eating diets that contained less carbohydrate than hunter-gatherers living in desert and tropical grasslands (6).
There’s a lot of debate regarding the macronutrient distribution of preagricultural human diets, and the aforementioned macronutrient estimates have later been put into question by other researchers. What we do know for sure is that hunter-gatherer diets generally were higher in protein and lower in carbohydrate than the typical diet consumed in industrialized nations today. This statement is supported by several lines of evidence (7, 8), including an analysis of subsistence data from 229 worldwide hunter-gatherer societies which show that the most plausible percentages of total energy from the three macronutrients would be 19–35% for protein, 22–40% for carbohydrate, and 28–58% for fat (8). It would have been difficult, if no impossible, for Paleolithic hunter-gatherers to eat as much starch and sugar as most people do today, because they didn’t eat grains, at least not in large quantities, or processed food.
Preagricultural human diets are often classified as low-carbohydrate, high-protein diets, as they tend to be lower in carbohydrate and markedly higher in protein than modern diets. However, when we take into account the fact that we lived as hunter-gatherers throughout the vast majority of our genus’ evolutionary history, it becomes clear that it’s more accurate to label the typical macronutrient ratio of hunter-gatherer diets as the “baseline”, and a diet that contains 50-60% carbohydrate and 10-15% protein as a high-carbohydrate, low-protein diet.
Should we let the macronutrient ratio of preagricultural human diets guide the planning of our modern diets?
Just because hunter-gatherers typically eat/ate a diet that is relatively high in protein and low in carbohydrate (but hign in fiber) doesn’t immediately lead to the conclusion that this is the way to go for optimal health. First of all, as previously mentioned, some traditional people have maintained very good health while eating diets with a macronutrient distribution that falls outside of the hunter-gatherer “norm”. Secondly, we have to consider the fact that we don’t have access to the same foods as our primal forebears, and that a lot of people these days adhere to exercise regimens that differ markedly from Paleolithic physical activity patterns.
That said, as everyone in the ancestral health community knows, it’s always wise to consider the evolutionary evidence when we go about planning our modern diets. When we combine an evolutionary template with modern nutritional science, it becomes clear that the dietary pattern of our ancient ancestors serves as a very good model for designing a healthy, well-balanced diet in the 21st century.
Over the years I’ve written several articles in which I’ve taken an in-depth look at what the scientific research tells us about how much protein, carbohydrate, and fat we should consume. Here are some of the key takeaways from these articles:
- The estimated macronutrient values of hunter-gatherer diets match well with what you get from a diet that contains a balanced proportion of animal source foods, fruits, vegetables, nuts, healthy fats, etc.
- The average Joe eats way too much bread, pasta, breakfast cereals, pastries, and other grain-based foods and would probably benefit greatly from replacing some of these foods (in particular the ones that primarily contain refined grains) with more nutrient dense foods such as grass-fed meat, eggs, fish, and vegetables. When you don’t eat a lot of grains and processed food, it’s difficult to derive more than approximately 40-50% of your energy from carbohydrate, unless you eat tuberous root vegetables and/or sugary fruits all day long.
- Protein has a potent effect on thermogenesis and satiety, and studies have shows that “high-protein” diets (>20%) are effective in the prevention and treatment of a range of health problems, in particular metabolic disorders and obesity (3) . This doesn’t mean that you have to eat a lot of protein, however, there is little doubt that there are many health benefits associated with a protein intake that is higher than the average intake of approximately 15% (of total calories) in the U.S. today.
- Public dietary guidelines in the U.S. and most other industrialized nations advocate that people should derive about 45-65% (the exact number differs from country to country) of their calories from carbohydrate. This idea, that we should all eat a diet that is high in carbohydrate, lacks proper scientific support. A growing amount of scientific data suggests that a lot of people, in particular those who are overweight and/or insulin resistant, benefit from adopting a diet that contains somewhat less carbohydrate than this (9, 10, 11). That said, it’s important not to go too low either, as a diet that is very low in carbohydrate often contains less than optimal amounts of fermentable fiber and can compromise an individual’s ability to maintain high levels of physical activity.
The macronutrient ratio doesn’t necessarily tell us that much about the healthfulness of the diet
The macronutrient distribution of a diet merely gives us a broad overview of what the diet consists of. To really be able to design a healthy diet we also have to consider fatty acid composition, indigestible vs. digestible carbohydrates, types of carbohydrates, food choices, food quality, etc. Personally, I think there is too much focus on macronutrient intake in the health & fitness community and too little focus on the previously mentioned factors. The fact that traditional people around the world have thrived on diets with very different macronutrient ratios further highlights the importance of looking at the bigger picture of things.
What is especially important to mention is that hunter-gatherers typically consume a lot more fiber than we do today, in large part because uncultivated fruits and vegetables are more fibrous than domesticated versions. This has important implications for the macronutrient composition of the diet, as indigestible (to the human host) carbohydrates are fermented by gut bacteria in the colon to produce short-chain fatty acids, meaning that these fermentable carbohydrates actually provide energy in the form of fats. This further highlights the discrepancy between the carbohydrate content of “modern diets” and hunter-gatherer diets; a discrepancy characterized by a markedly lower net carbohydrate intake among hunter-gatherers.
My general recommendations
- Protein: Eat moderate amounts of high-quality protein at every meal. Most people, particularly those who want to lose weight and/or gain muscle, would benefit from getting at least >20% of their total calories from protein. Homo sapiens, as well as many other animal species, have evolved a strong appetite for protein. If you eat a well-balanced diet, are in good health, and know how to listen to the signals your body is sending you, your appetite should naturally steer you towards an adequate intake of protein. Stick to grass-fed, organic, and/or wild animal products whenever possible.
- Carbohydrate: Eat plenty of plant foods that are rich in fermentable fibers (e.g, onions, leeks). Adjust your intake of simple sugars and starch according to your physical activity levels. Athletes who perform a lot of anaerobic exercise typically require quite a bit of starch in their diet to perform optimally, whereas sedentary individuals – particularly those who are insulin resistant and/or overweight – often do best on a diet that is lower in starchy foods, particularly bread, pasta, breakfast cereals, and the like. Good sources of starch includes foods such as sweet potatoes, yams, and brown rice. A carbohydrate intake of 20-45% (of total daily calories) is a good fit for most people.
- Fat: Include healthy fats in every meal. Foods such as avocados, eggs, salmon, and olives are superior to non-paleo foods such as cream, GHEE, cheese, butter, and bacon.