18 . 01 . 2019
Metabolic Lessons from our Ancestors
The modern era is characterized by unprecedented scientific and technological development. However, we are faced with a high prevalence of chronic diseases that did not affect our ancestors. Are we as a society doing something wrong?
To address this question, an interesting study was published that analyzed the main differences in diet, lifestyle and indicators of metabolic health between groups of hunter-gatherers and the western industrialized population.
Fortunately, there are still a few small-scale societies scattered around the globe that eat, move and relate to each other, in a similar way to our ancestors who inhabited the planet 10,000 years ago. The following populations are such examples:
- the Hadza people who inhabit northern Tanzania and represent the last known strictly hunter-gatherer group on the planet. Their diet is composed exclusively of meat, tubers, fruit and honey.
- the Tsimané of the Bolivian Amazonia, who in addition to hunting and fishing also practice subsistence farming, cultivating cassava and plantains.
What these and other ancestral populations have in common is a near zero incidence of cardiovascular disease, diabetes mellitus and obesity, in contrast to what happens in the industrialized world.
What is the life expectancy in these populations?
Often these anthropological data are discarded under the premise that these individuals do not develop the diseases of modern civilization simply because they do not live to an advanced age. It is true that the average life expectancy is reduced in these populations, in the range of 30-40 years, and the infant mortality rate is very high, but some of these individuals live up to 70-80 years old. The main cause of death is acute disease (typically infectious and gastrointestinal), followed by trauma.
Fig. 1 – The Hadza are an indigenous population living in Tanzania, composed of approximately 1000 individuals.
What is the percentage of obesity?
Obesity is a very rare phenomenon in these populations. In the Hadza, for example, mean BMI (body mass index) is 20 for both genders and only 2% of individuals fall into the overweight category (BMI between 25 and 30). The Tsimané have a higher mean BMI (24.7 for women and 23.8 for men) but reduced body fat percentages, which suggests that BMI may not be a reliable measure of body adiposity in these cases.
Is there cardiovascular disease in these populations?
Cardiovascular disease appears to be a negligible cause of death in the hunter-gatherer societies, even in individuals over 60 years of age. Hypertension, which affects more than 60% of the US population over 60, is also an uncommon condition.
A 2017 study sought to identify the presence of coronary artery atherosclerosis assessed by calcium scores and the results were the lowest ever reported in any population to date.
The lipid profile and glucose levels of the hunter gatherers are also much more favorable.
Fig. 2 – Lipid and glycemic profile of two populations of hunter gatherers in comparison to the North American population.
What is their physical activity and energy expenditure?
As expected, these populations are much more physically active than in the western developed world. Women walk an average of 9.5 km and men 14.1 km per day. In addition, they engage in variable peaks of more vigorous activity as needed. These high levels of physical activity are not offset by increased time resting, averaging 5.9-7.1 hours of sleep per night.
Surprisingly, although hunter-gatherer physical activity is considerably higher, their total energy expenditure per day is similar to that of industrialized Western populations. Therefore, the human body appears to have an energy efficiency mechanism, whereby energy consumption remains relatively stable despite variations in physical activity.
This observation allows us to infer that hunter-gatherers have a lower rate of obesity not because they spend more energy, but because they ingest less calories.
What do their diets consist of?
The food ingested by the various hunter-gatherer populations varies significantly according to what Nature offers. For example, the higher the latitude, the higher the animal protein intake, probably due to the greater scarcity of plant matter. In parallel, the macronutrient ratio that makes up the diet also varies considerably between different hunter gatherer and small-scale societies. However, an interesting factor to note has to do with the consumption of carbohydrates, including sugars in the form of honey. In fact, the diets of the Tsimané and the Hadza are richer in carbohydrates than the average of the industrialized populations. This observation runs counter to the carbohydrate vilification theory defended by some groups.
There are several similarities between these “ancestral” diets, which can be summarized in the following topics:
- Include meat and/or fish and plant foods.
- Preference for cooked food.
- Micronutrient rich (minerals, vitamins, antioxidants, etc.).
- Low glycemic index (ability of a given food to raise blood glucose when ingested).
- Abundant consumption of fiber.
Fig. 3 – Diet composition (percentage of daily calories derived from each macronutrient) of two populations of hunter gatherers in comparison to the North American population.
Evolutionary anthropology is the discipline that studies how human physiology and behavior has adapted to Nature throughout history. It is fascinating how we can have so much to learn from ancestral civilizations that seem to be completely “outdated.” Medicine has evolved in an extraordinary way, allowing us to control and eradicate some infectious diseases and to treat many other pathologies, which lead to an increase in life expectancy. But we haven’t done everything right and the study of our “ancestors” can show us which adjustments to (re)implement.
Pontzer H, Wood BM, Raichlen DA. Hunter-gatherers as models in public health. Obesity Reviews 2018; 19 (December): 24-35.
KaplanH, Thompson RC, Trumble BC et al. Coronary atherosclerosis in indigenous South American Tsimane: a cross-sectional cohort study. Lancet 2017; 389: 1730–1739.