Exercise

A media review found that hundreds of articles claim that long periods of sitting every day are comparable to smoking. That is certainly not true. It is assumed that smoking will claim a billion lives in this century. Tobacco use is responsible for at least a tenfold greater risk of death: among the heaviest smokers there are 20 additional deaths per 1000 people each year, and among the most extreme sitters it is fewer than two. Even if someone smokes very little—just a few cigarettes a day—that is associated with a higher risk. The good news is that you can still increase your lifespan by several years even if you do not quit smoking until age 65.

The decline in tobacco use is one of the great victories of our health care system. The share of adult smokers fell from 42 percent in 1965 to only 14 percent today. Cigarettes now kill only about half a million Americans a year; our diet, by contrast, kills many thousands more. To be victorious with diet as well, it has been suggested that a plant-based diet be regarded as the “dietary equivalent of quitting smoking.”

Exercise

When people retire, they do not change their diet, but they become more active. For many, leaving the workforce means having more time for activities such as sports and gardening, or inviting friends and family over more often. What role could physical activity play in longevity? When it comes to ways to slow aging, aerobic exercise can trigger autophagy, lower inflammation markers, and also reduce DNA damage and promote its repair, although all of that may not influence aging if you factor out weight loss. But there is clear evidence that exercise plays a role in how well we function when we are old. A meta-analysis of cohort studies among middle-aged and older people with 20-year follow-ups found that adults who exercised were more likely to age successfully than those who sat a lot, although fewer than 3 percent of those over 60 exercised as much as recommended.

Exercise is Medicine

Population studies showed a correlation between regular aerobic exercise and a reduced risk of at least 35 different diseases, but what did intervention studies show regarding cause and effect? Randomized controlled trials with older adults showed that physical activity can improve muscle mass, strength, balance, and mobility; it also lowers the risk of falls and thus the danger of bone fractures, while minimizing bone loss. It has also been shown that exercise improves cognitive abilities, lifts mood, and helps depression just as well as the prescription antidepressant Zoloft. Exercise helps with erectile dysfunction and improves our overall quality of life. The evidence base for the general health benefits of exercise is overwhelming. More about its benefits in aging at see.nf/perks.

Who should ask their doctor first?

If you are a man over 45 or a woman over 55, have diabetes, or have symptoms such as chest pain, dizziness, or shortness of breath, I would recommend speaking with your doctor before you start exercising.

Survival of the Fittest?

Researchers paid by Coca-Cola describe lack of exercise as the “biggest public health problem in the 21st century.” That is not true. Exercise is great, but in terms of risk factors for death and disability in the United States, lack of exercise is in tenth or eleventh place. Worldwide, lack of exercise does not even come close to making the top 20 in terms of years of healthy life lost. As I have already explained, poor diet is by far our biggest killer, followed by smoking.

Exercise has been described as an “intervention proven to substantially affect average and maximum lifespan in humans.” You can find a comprehensive review at see.nf/lifelongexercise. But whether physical inactivity is responsible for 6, 9, or even 15 percent of premature mortality—all of these estimates come from observational studies and are based on an assumption of cause and effect. I was surprised to see the degree of controversy in the medical literature about whether there is any discernible benefit of exercise for longevity at all. You can imagine the confounders and the potential for reverse causation. I discuss some of the critical studies at see.nf/fitnesslongevity.

For example, researchers compared the effects of physical activity during leisure time with that at work. If the relationship between exercise and a high life expectancy is truly causal, the context in which one moves should not matter. As you probably suspect, physical labor is associated with a shorter life, not a longer one, which again shows the primacy of confounders such as socioeconomic factors.

Can we extend our lifespan with exercise?

Could a genetic predisposition to physical fitness influence the exercise/longevity relationship more than the physical activity itself? A trial with two groups of rats investigated this question—one bred to be able to run for a very long time, the other with the opposite trait. When the animals were given running wheels, something unexpected happened: in both groups, longevity decreased. Through voluntary exercise, the rats shortened their lives.

Twin studies can show that people, too, have a genetic predisposition to exercise. When identical twins move out of their parents’ home and live their own lives, it is much more likely than with fraternal twins that they will exercise similar amounts—that is, if one works out a lot, the other does too—if they have 100 percent identical DNA and not just 50 percent like ordinary siblings. But if you look at the rare cases of identical twins whose exercise habits differ, you can tell whether longevity is genetically predisposed or whether it is due to exercise. Does intense physical activity matter for two people with the same DNA? Apparently not. Identical twins have the same mortality rate, regardless of whether they exercise or not.

So does exercise confer a longer life or not? A critical analysis concluded that “it still needs to be investigated whether the undisputed health benefits of exercise stand in a demonstrable causal relationship to longevity.” Learn more at see.nf/exerciselongevity.