This article is an excerpt from the Shortform book guide to "Lifespan" by David Sinclair. Shortform has the world's best summaries and analyses of books you should be reading.
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Is aging an incurable disease? Or can aging be treated?
Scientists are moving to the idea that aging is not, in fact, an inevitable doom that we’ve so far believed it to be. Rather, aging is a treatable disease. Biologist David Sinclair suggests a number of different ways to treat aging, either by delaying the symptoms or (in some cases) actually reversing the damage.
Here’s how to reverse aging, according to David Sinclair.
Aging Can Be Treated and Reversed
According to biologist David Sinclair, aging is a disease that can be treated, and we are slowly but surely getting there. In his book Lifespan, he discusses how to reverse aging and extend both lifespan and healthspan.
Take Advantage of Hormesis
Sinclair says that we can prolong our own life and health through hormesis: A phenomenon by which our bodies become stronger in response to stressors like hunger, extreme temperatures, and physical damage. Hormesis activates numerous survival mechanisms, such as conserving resources and repairing cellular damage. Sinclair believes we can take advantage of hormesis not just to extend our lives, but to improve our quality of life as well.
We already employ hormesis in several ways, such as dieting, exercising, and sitting in saunas. However, Sinclair says that recent and upcoming scientific advancements will allow us to control these processes more effectively and efficiently—for example, we might be able to use an injection to strengthen our muscles without the need for exercise.
(Shortform note: In Antifragile, Nassim Nicholas Taleb tells us that the toxicologist Hugo Schulz first discovered hormesis when he noted that small doses of particular toxins would actually cause yeast cells to grow and reproduce more quickly—though higher doses would kill the yeast as expected. From this, we can see that hormesis has limits; the key is to use mild stressors, like hunger, instead of severe stressors like starvation.)
Sinclair recommends intermittent fasting (IF) as a way to trigger your body’s stress responses without causing malnutrition. He suggests several different variations of IF, saying that it’s currently unclear which method is best, but all are beneficial:
- Set aside 8 hours a day where you’re allowed to eat, and fast the rest of the time (the 16:8 method).
- Reduce your calorie intake by 75% for 2 days a week (the 5:2 method).
- Eat no food for a week once per quarter.
Sinclair also says that a vegetarian diet can activate hormesis. The relatively low levels of certain proteins (as compared with meat) can trigger our survival mechanisms in the same way that calorie restriction does.
(Shortform note: In addition to triggering hormesis, vegetarian diets tend to be relatively low in fat, sodium, sugar, and cholesterol compared to meat-heavy diets. Scientists believe that a vegetarian diet reduces the chance of heart disease, cancer, and diabetes, lowers blood pressure, and strengthens bones.)
Finally, Sinclair says that exercise (which, by definition, puts stress on our bodies) can greatly extend our lifespans. For example, researchers have found that exercise lengthens and protects telomeres. Telomeres are small complexes of DNA and proteins at the ends of our chromosomes that get shorter each time a cell divides. When the telomere runs out, the cell stops dividing—leading to many of the problems of old age. Therefore, lengthening telomeres can literally keep our bodies younger for longer.
Sinclair adds that exercising in low temperatures appears to boost the youthening effects of exercise, most likely due to combining the stress of working out with the stress of being exposed to cold.
(Shortform note: It doesn’t take a lot of exercise to significantly improve your health. Researchers found that 150 minutes (two and a half hours) of moderate exercise each week increased life expectancy by about seven years, and that active 70-year-olds had hearts, lungs, and muscles that were as strong as some 40-year-olds’.)
Killing Senescent Cells to Preserve Other Cells
As we get older, our cells start to shut down, which causes a lot of the deterioration that we experience as we age. Sinclair believes that destroying those cells before they cause too much damage can significantly extend both life and health.
Cells that are no longer able to divide, or that suffer genetic or epigenetic damage too severe to repair, can enter senescence: They don’t function anymore, but they also don’t die when they should (leading some researchers to refer to them as “zombie cells”). Furthermore, senescent cells can cause other cells to enter senescence, so the process only accelerates once it’s begun.
Sinclair says that senescent cells send out chemicals that cause inflammation in surrounding tissue, which is associated with symptoms of aging. Therefore, it seems likely that senescent cells are responsible for many of the negative effects of old age.
Researchers found that destroying senescent cells in mice extended their remaining lifespans by a third or more and reversed many of the effects of aging; in theory, the same principle should apply to humans. To that end, researchers began testing senolytics (“senescence destroyers”) on people in 2018, though Sinclair says it could be years before we have any conclusive results about their effectiveness and safety for human patients.
Protecting Health With Technology
While the focus of Sinclair’s work is undoing the damage caused by aging, he also believes that technology will extend our years of health by letting us recognize and treat diseases before the symptoms even begin. Improved DNA sequencing techniques will allow us to find genetic markers and risk factors for numerous conditions, while biometric devices (like smartwatches) can track our vital signs and warn us of potential problems. Furthermore, Sinclair believes that having access to this detailed information will allow experts to design diets, exercise programs, and treatment regimens that are custom-tailored to your genetics and lifestyle.
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Here's what you'll find in our full Lifespan summary :
- Why biologist and geneticist David Sinclair believes old age is a curable disease
- The potential problems of a world where people never die
- How the elderly stifle the economy
