David Sinclair: Fasting and Its Benefits

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 it true that fasting can make you live longer? How does fasting promote longevity?

According to Australian biologist David Sinclair, fasting can help slow down aging and extend healthspan. This is because fasting triggers hormesis—the process by which your body becomes stronger by repairing cellular damage and activating other survival mechanisms.

Here’s how fasting can turn the biological clock, according to Sinclair.

David Sinclair: Fasting Can Turn the Biological Clock

According to David Sinclair, fasting triggers your body’s stress responses without causing malnutrition. He suggests several different variations of IF (intermittent fasting), saying that it’s currently unclear which method is best, but all are beneficial:

  1. Set aside 8 hours a day where you’re allowed to eat, and fast the rest of the time (the 16:8 method).
  2. Reduce your calorie intake by 75% for 2 days a week (the 5:2 method). 
  3. 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. 

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.

How to Fast Safely

Johns Hopkins Medicine notes that, while IF can have numerous health benefits, it’s not for everyone. They say that the following people should not attempt intermittent fasting:

– People under 18 years old
– Pregnant or breastfeeding women
– People with metabolic disorders like diabetes
– People who suffer from eating disorders

Furthermore, if you do try IF remember that you can drink water and other zero-calorie drinks (such as black tea or coffee) during your fast periods. It’s important to stay hydrated while fasting. 

David Sinclair: Fasting and Its Benefits

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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

Darya Sinusoid

Darya’s love for reading started with fantasy novels (The LOTR trilogy is still her all-time-favorite). Growing up, however, she found herself transitioning to non-fiction, psychological, and self-help books. She has a degree in Psychology and a deep passion for the subject. She likes reading research-informed books that distill the workings of the human brain/mind/consciousness and thinking of ways to apply the insights to her own life. Some of her favorites include Thinking, Fast and Slow, How We Decide, and The Wisdom of the Enneagram.

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