Fasting and longevity

Fasting and Longevity: Lessons from David Sinclair's Lifespan

In his book Lifespan (2019), Dr. David A. Sinclair, a Harvard University geneticist and one of the most influential figures in longevity science, proposes that aging is not an inevitable process but a disease that can be prevented and even reversed. One of the pillars of his approach to slowing down aging is intermittent fasting and temporary caloric restriction, practices that stimulate key genetic mechanisms promoting cellular repair, regeneration, and survival.

Why is Fasting Important, According to Sinclair?

Sinclair explains that when the body enters a state of energy scarcity (such as during fasting), ancestral survival genes are activated, improving cellular health. This shift activates sirtuins, a group of proteins that regulate functions like DNA repair, inflammation, genomic stability, and metabolism. Sirtuins require NAD+ (nicotinamide adenine dinucleotide) to function, a molecule that also naturally increases during fasting and exercise (Sinclair, 2019, pp. 86–95).

Fasting also stimulates processes like autophagy, through which cells recycle damaged or old components, and activates mitochondrial biogenesis, increasing the production of new mitochondria. This directly leads to higher energy levels, better glucose control, and reduced systemic inflammation.

How to Practice Fasting Safely

In Lifespan, Sinclair doesn't prescribe a single fasting method but emphasizes that any degree of intermittent caloric restriction has benefits. Personally, he practices a daily intermittent fasting pattern: he eats a late breakfast or simply skips it, concentrating his meals into a 6–8 hour window each day. This practice is known as the 16/8 fast, where you fast for 16 hours and eat during an 8-hour window.

For beginners, Sinclair recommends starting gradually: delaying breakfast and avoiding unnecessary snacks, especially ultra-processed ones. The approach should be sustainable and aligned with your individual lifestyle. He also suggests combining fasting with a plant-based diet low in animal protein and rich in compounds like resveratrol, which he himself supplements with and which mimics some of the effects of fasting (Sinclair, 2019, p. 103).

Observed Benefits

In addition to promoting cellular longevity, intermittent fasting improves insulin sensitivity, reduces blood pressure, enhances mental clarity, and optimizes lipid metabolism. Sinclair emphasizes that it's not about simply living more years, but about extending functional youth and delaying the onset of chronic diseases like Alzheimer's, cancer, or type 2 diabetes.

Bibliographical Reference:

Sinclair, D. A., & LaPlante, M. (2019). Lifespan: Why We Age—and Why We Don’t Have To. Atria Books.