To what degree does regular exercise beyond the recommended minimum of 30 minutes a day improve long-term health and life expectancy? This and related questions on the shape of the dose-response curve for aerobic exercise remain open for debate. It is clear that being sedentary has a cost in terms of health and life expectancy, and the balance of evidence to date suggests that the 80/20 point for benefits due to exercise is found somewhere higher than the generally recommended level. Yet it is unclear as to whether professional athletes, who tend to live longer than the general population, live longer because of the high levels of exercise or because they also tend to be more robust individuals who would have enjoyed greater longevity regardless of profession. While it remains to put good numbers to much of the dose-response curve for exercise, this study of the Hadza people adds to the evidence for additional benefits to accrue to those who go beyond 30 minutes a day:
The Hadza live a very different kind of lifestyle - and a very active one, engaging in significantly more physical activity than what is recommended by U.S. government standards. They also have extremely low risk of cardiovascular disease. Researchers have spent several years studying the lifestyle of the Hadza. "Our overall research program is trying to understand why physical activity and exercise improve health today, and one arm of that research program aims to reconstruct what physical activity patterns were like during the evolution of our physiology. The overarching hypothesis is that our bodies evolved within a highly active context, and that explains why physical activity seems to improve physiological health today."
The U.S. Department of Health and Human Services recommends that people engage in 150 minutes per week of moderate intensity activity - about 30 minutes a day, five times a week - or about 75 minutes per week of vigorous intensity activity, or an equivalent combination of the two. However, few Americans achieve those levels. The Hadza, on the other hand, meet those weekly recommendations in a mere two days, engaging in about 75 minutes per day of moderate-to-vigorous physical activity, or MVPA. Furthermore, and consistent with the literature identifying aerobic activity as a key element necessary to a healthy lifestyle, researchers' health screenings of Hadza people have shown that the population has extremely low risk for heart disease. "They have very low levels of hypertension. In the U.S., the majority of our population over the age of 60 has hypertension. In the Hadza, it's 20 to 25 percent, and in terms of blood lipid levels, there's virtually no evidence that the Hadza people have any kind of blood lipid levels that would put them at risk for cardiovascular disease."
While physical activity may not be entirely responsible for the low risk levels - diet and other factors may also play a role - exercise does seem to be important, which is significant because humans' physical activity levels have drastically declined as we have transitioned from hunting and gathering to farming to the Industrial Revolution to where we are today. "Over the last couple of centuries, we've become more and more sedentary, and the big shift seems to have occurred in the middle of the last century, when people's work lives became more sedentary. In the U.S., we tend to see big drop-offs in physical activity levels when people age. In the Hadza, we don't see that. We see pretty static physical activity levels with age. This gives us a window into what physical activity levels were we like for quite a while during our evolutionary history, and, not surprisingly, it's more than we do now. Perhaps surprisingly, it's a whole lot more than we do now. Going forward, this helps us model the types of physical activity we want to be looking at when we explore our physiological evolution. When we ask what kinds of physical activity levels would have driven the evolution of our cardiovascular system and the evolution of our neurobiology and our musculoskeletal system, the answer is not likely 30 minutes a day of walking on a treadmill. It's more like 75-plus minutes a day."