The American Journal of Medicine
Volume 123, Issue 12 , Pages 1082-1086, December 2010

Achieving Hunter-gatherer Fitness in the 21st Century: Back to the Future

  • James H. O'Keefe, MD

      Affiliations

    • Mid America Heart Institute/University of Missouri-Kansas City, Kansas City
    • Corresponding Author InformationRequests for reprints should be addressed to James O'Keefe, MD, Cardiovascular Consultants, Mid America Heart Institute, 4330 Wornall Rd., Ste. 2000, Kansas City, MO 64111
    • ,
  • Robert Vogel, MD

      Affiliations

    • University of Maryland, College Park
    • ,
  • Carl J. Lavie, MD

      Affiliations

    • Ochsner Clinic, Jefferson, La
    • ,
  • Loren Cordain, PhD

      Affiliations

    • Colorado State University, Fort Collins

published online 14 September 2010.

Article Outline

Abstract 

The systematic displacement from a very physically active lifestyle in our natural outdoor environment to a sedentary, indoor lifestyle is at the root of many of the ubiquitous chronic diseases that are endemic in our culture. The intuitive solution is to simulate the indigenous human activity pattern to the extent that this is possible and practically achievable. Suggestions for exercise mode, duration, intensity, and frequency are outlined with a focus on realigning our daily physical activities with the archetype that is encoded within our genome.

Keywords: Cardiovascular health, Cross-training, Evolution, Exercise, Fitness, Hunter-gatherer, Obesity, Prevention

 

Physical activity is decreasing in our society, especially in children as they mature.1 Clear evidence suggests that physical activity has numerous favorable beneficial physiologic effects that result in demonstrable reductions in cardiovascular and other disease endpoints. Daily exercise substantially alters the expression of a substantial proportion of the genes that comprise the human genome.2, 3 These profound and far-reaching changes in genetic expression may explain why cardiovascular fitness and daily energy expenditure on physical activity are among the strongest correlates of long-term health and survival2, 3, 4, 5, 6, 7 (Figures 1, 2).

Clinical Significance

 


•Humans remain genetically adapted for a very physically active hunter-gatherer lifestyle. Many of the health problems endemic today result from lifestyle that is at odds with this evolutionary milieu.

•The daily physical activity pattern of the hunter-gatherer is an ideal template from which to design a modern exercise regimen.

•Characteristics include: incorporation of physical activity into daily life wherever possible, interval and strength/flexibility training, outdoor exercise on natural surfaces, group exercise, ample time for rest/recovery, and lifelong fitness.

Reproduced with permission.

Reproduced with permission.

From the inception of the human genus, Homo, approximately 2.4 million years ago,8 our ancestors lived as hunter-gatherers for approximately 84,000 generations.9 Survival within the hunter-gatherer niche required a large amount of daily energy expenditure in activities such as food and water procurement, social interaction, escape from predators, and maintenance of shelter and clothing. This lifestyle represents the exercise patterns for which we remain genetically adapted. Accordingly, humans are superbly capable of performing the wide array of physical actions and behaviors required of the hunter-gatherer. Quantum improvements in technology such as those that spawned the agricultural revolution (350 generations ago), the industrial revolution (7 generations ago), and the digital age (2 generations ago) have engendered large systematic reductions in the amount of physical work required by humans.10, 11 Nonetheless, our innate exercise capabilities and requirements that evolved via natural selection over thousands of millennia remain essentially the same as for our Stone Age ancestors. Marked deviation from those indigenous exercise patterns predictably results in physical disability and disease. An understanding of the typical hunter-gatherer physical activity pattern would seem to be an ideal template from which to design a modern exercise program.

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Fitness for Life in the Wild 

Ironically, today, as the last vestiges of the hunter-gatherer lifestyle are being eclipsed by modern civilization, science is coming to realize the importance of this way of life for current-day human health, and its relevance to optimal fitness in the 21st century.12, 13 Compared with the glacial pace of genetic evolution, human technological and social evolution has occurred at light speed. This discordance has left us genetically adapted for the rigors of life as a hunter-gatherer despite the fact that we are citizens of the high-tech, sedentary, overfed, emotionally stressed 21st-century world. The intuitively obvious solution to this conundrum is to simulate the activity patterns of our Pleistocene ancestors.

Natural selection endowed us with the genetic makeup that allowed our ancestors to not only survive the physical work and daily rigors required of the hunter-gatherer but, to thrive in response to these demands.14 Our ancient ancestors evolved an instinct compelling them to “Move when you have to, and rest when you can.” Many of their waking hours were necessarily consumed with the physical activities required of everyday life (Table 1).15 Except for the very young or the very old, everyone did a wide range of manual labors on a daily basis. Their activities of daily life were all the “exercise” that Stone Age people would have ever needed to maintain superb general fitness.16 Instincts to preserve energy and strength for these requisite physical chores conferred survival advantages to hunter-gatherers. However, this inborn proclivity to take the path of least resistance plays a major role in the health woes beleaguering modern Americans.

Table 1. Energy Expended: Hunter-Gatherer vs Moderns15
SpeciesSexWeight kgRMR kcalTEE kcalRatio (TEE/RMR)EE PA kcalDay Range km
Fossil hominids
Homo habilis 48.0140423871.70983
Homo erectus 53.0151727311.801214
Homo sapiens (early) 57.0160528801.801284
Modern hunter-gatherers
KungM46.0127521781.7190310
F41.0117017701.516008
AcheM59.6154933272.15177816
Acculturated modern humans
Homo sapiensM70.0169420001.183062.4
(office worker)⁎F55.0144816791.162312.4
Homo sapiens (runner)†M70.0169428881.70119411

EEPA=energy expenditure attributed to physical activity; RMR=resting metabolic rate; TEE=total energy expenditure.

⁎Sedentary office worker (4).

†Runner running 12.1 km/h (4).

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Ideal Exercise Patterns 

The prospective clinical trials that have been performed assessing the health effects of various exercise regimens and the observational data are generally supportive of the health benefits conferred by a hunter-gatherer style of fitness regimen. A growing body of data indicates that many of the benefits of exercise accrue at relatively low to moderate levels of exercise.17 Continuous higher-level activity, such as jogging 32 km/week, was not found to be statistically better than walking 19 km/week for reducing features of the metabolic syndrome.18 On the other hand, a daily regimen of at least 45 minutes and possibly up to 90 minutes per day of cumulative physical activity is necessary for most overweight or obese individuals to achieve and maintain ideal body weight.19 The 10,000 steps per day concept emphasizes the importance of total daily energy expenditure. This fitness strategy generally involves walking at a modest pace intermittently throughout the day.20 Combined aerobic and resistive activity has been shown to be superior to either alone for improving glycemic control for individuals with type 2 diabetes.21 Intermittent intense activity results in more weight loss and better glucose metabolism than equivalent amounts of lower-intensity continuous activity.22

Even though exercise in general confers powerful cardiovascular protection,23 some evidence suggests that physical activity performed outside may be more beneficial than indoor exercise.24 Outdoor exercise offers the opportunity for sunlight exposure, which stimulates vitamin D synthesis in the epidermis. Vitamin D deficiency is a common and potent risk factor for many health problems, including cardiovascular disease.25 Outdoor exercise reduces emotional stress and enhances compliance to a daily fitness regimen better than indoor exercise.26, 27

Although hunter-gatherer women rarely participated in large-game animal hunting,28 they too were very physically fit as a result of the demands of their daily physical routines. Ethnographic accounts of hunter-gatherers indicate that women typically went out foraging to collect food every other or every third day. Women, usually in groups, spent hours walking to and from sources of food, water, and wood.4 Additionally, these forager women were often carrying their children for extended distances as well. Anthropologists have estimated that the typical hunter-gatherer mother carried her child until about age 4 years, covering upwards of 4,800 km with the child in her arms over this period of time.29

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Rest and Cross-Training 

Hunter-gatherers would have likely alternated difficult days with less demanding days when possible.16 Their routines called for endeavors that promoted aerobic endurance, flexibility, and strength; thereby bestowing them with multi-faceted fitness that would have also conferred resiliency and reduced the likelihood of injury. The same pattern of alternating a strenuous workout one day with an easy one the next day produces higher levels of fitness with lower rates of injury.30 In exercise physiology, it has been well documented that aerobic capacity within an individual may increase based upon exercise frequency, intensity, and duration.31 Of these 3 factors, intensity is the most important feature in optimizing the aerobic capacity, especially in an already trained individual.31 The natural cross-training that was a mandatory aspect of life as a hunter-gatherer has been found to improve performance across many athletic disciplines. Now, most endurance sport coaches incorporate cross-training such as strength and flexibility exercises into their prescribed training routines.32, 33, 34

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The Dangers of Excessive Exercise and Inadequate Rest 

Whereas physical exercise is unquestionably protective, there are evolving data from Vogel et al35 and others that extreme physical activity may be detrimental to cardiovascular health. Prolonged and excessive aerobic exercise efforts such as marathons, ultra-marathons, full-distance triathlons, and very-long-distance bicycle rides are inconsistent with our genetic heritage. The pattern of exercise for which we are genetically adapted involves a diversity of activities performed intermittently, at moderate intensities and moderate durations. Even in highly trained individuals, high-intensity, multi-hour endurance exercise effort is associated with damage to the myocardial cells and connective tissue.36, 37, 38, 39

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Naturally Reestablishing Caloric Balance 

For all humans before the dawn of the Agricultural Revolution, energy input (food) and energy expenditure (physical activity) were directly and inextricably linked. When humans of the Pleistocene Age were hungry, they had to hunt, gather, forage, and fish.4 Hunger, or even the threat of inadequate food, instills a powerful motivation to move with intensity and purpose. The convenient modern world has virtually eliminated the evolutionary connection between energy expenditure and calorie ingestion. The “search and pursuit” time are minimized, while the caloric payoff is almost unlimited. Today, the acquisition of massive amounts of calorie-dense foods and beverages requires minimal energy expenditure.

This systematic and pervasive disconnect between energy intake and energy expenditure inherent in modern cultures is a fundamental factor in the obesity epidemic. Increasing reliance on pharmaceutical agents to counteract this problem is much less logical than simply realigning our lifestyle to be more physically active, (Table 2) and our diet to include more unprocessed, naturally low-calorie, whole foods in order to correct this energy imbalance.40

Table 2. Caloric Cost of Various Hunter-gatherer or Forager Activities and Recommended Equivalent Modern Activities4
Hunter-Gatherer ActivityModern Equivalent ActivityCaloric Expenditure (Kilocalories/Hour)
176-lb Man132-lb Woman
Carrying logsCarrying groceries, luggage893670
Running (cross country)Running (cross country)782587
Carrying meat (20 kg) back to campWearing backpack while walking706529
Carrying young childCarrying young child672504
Hunting, stalking animalsInterval training619464
Digging (tubers in field)Gardening605454
Dancing (ceremonial)Dancing (aerobic)494371
Carrying, stacking rockLifting weights422317
Butchering large animalSplitting wood with axe408306
Walking – normal pace (fields and hills)Walking – normal pace (outside on trails, grass, etc.)394295
Gathering plant foodsWeeding garden346259
Shelter constructionCarpentry, general250187
Tool constructionVigorous housework216162

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Characteristics of a Hunter-Gatherer Fitness Program 


1.A large amount of background daily light-to-moderate activity such as walking was required. Although the distances covered would have varied widely, most estimates indicate average daily distances covered were in the range of 6 to 16 km. The hunter-gatherers' daily energy expenditures for physical activity typically were at least 800 to 1200 kcal,41 or about 3 to 5 times more than the average American adult today.

2.Hard days were typically followed by an easier day. Ample time for rest, relaxation, and sleep was generally available to ensure complete recovery after strenuous exertion.

3.Walking and running were done on natural surfaces such as grass and dirt, often over uneven ground. Concrete and asphalt surfaces are largely foreign to our genetic identity.

4.Interval training sessions, involving intermittent bursts of moderate- to high-level intensity exercise with intervening periods of rest and recovery, should be performed once or twice per week.

5.Regular sessions of weight training and other strength and flexibility building exercises are essential for optimizing musculoskeletal and general health and fitness. These need to be performed at least 2 or 3 times per week, for at least 20 to 30 minutes per session.

6.Virtually all of the exercise was done outdoors in the natural world.

7.Much of the physical activity was done in context of a social setting (small bands of individuals out hunting or foraging). Exercising with one or more partners improves adherence and mood.23

8.Except for the very young and the very old, all individuals were, by necessity, physically active almost their entire lives.

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 Funding: There was no funding or compensation made in the writing of this article.

 Conflict of Interest: None.

 Authorship: All authors had access to the information and had a role in the writing of this manuscript.

PII: S0002-9343(10)00463-8

doi:10.1016/j.amjmed.2010.04.026

The American Journal of Medicine
Volume 123, Issue 12 , Pages 1082-1086, December 2010

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