Home body Lifespan: Why We Age — And Why We Don’t Have To

Lifespan: Why We Age — And Why We Don’t Have To

by Marianne Navada
lifespan why we age and why we don't have to

Title: Lifespan: Why We Age — And Why We Don’t Have To | Author: David A. Sinclair PhD.

The Main Points

Aging is a disease we can cure. If we cure aging, we cure other diseases such as cancer. Right now, our society and the healthcare industry treat aging as inevitable. This mindset needs to change. Based on the research on cellular behavior and the Information Theory of Aging, we know how and why we age. Put simply, we age because of the accumulation of senescent cells. This foundational knowledge allows us to not only reverse aging, but to stop or slow down the process.

A future where it’s common for people to live until 125 years old is within our reach. The author understands that living longer has personal and social implications, and with the right leadership and plan, having more time to spend alive and well holds great possibilities. 

Although written for a general audience, be prepared for some scientific words. Get ready to read about medical and lab studies on genetics and cellular reprograming, but also some personal stories from the author.

The author notes that he’s a researcher and not a medical doctor. The book doesn’t aim to give medical advice.

Our Cells Explain Why We Age

We age because of the accumulation of senescent cells. Senescent cells lose the “ability to divide, but refuse to die”, aptly referred to as “zombie cells”. Why are these zombie cells bad?  These cells release proteins that cause “inflammation, attract other cells that attack tissues”, and can “stimulate other cells to become a tumor and spread.” 

Why Do Senescent Cells Accumulate?

It boils down to our survival circuit and the Information Theory of Aging.  

Survival Circuit

When certain cells detect DNA break, reproduction and cell division stops temporarily. Cells instead work on repairing damaged DNA. Both internal and external factors can cause DNA breakage.

The survival circuit and the senescent cells evolve to protect us in our 30s and 40s, however eventually, they destroy us. This is referred to as “antagonistic pleiotropy”. “The idea that a survival mechanism that is good for us when we are young is kept through evolution because this far outweighs any problems in might cause when we get older.”

But why does the cycle of repair and reproduction, the survival circuit, eventually gets corrupted? The answer lies in the way the cells store information.

The Information Theory of Aging

Our cells constantly respond to our environment. This means a need for flexibility. The author compares our bodies to a computer. Our genome acts as the hardware and the epigenome, acts as the software. The epigenome orchestrates the way our cells behave. To respond to environmental changes, it needs a system of record keeping that is flexible, with an “unlimited number of possible values”. Eventually, information is lost after constant copying and mutation. 

The book argues that scientists currently treat aging by looking at different “hallmarks”, treating each one separately. However, treating aging through the lens of Information Theory of Aging allows us to have a singular answer that addresses all of these hallmarks.

Habits and Practices for Cellular Health

Aside from scientific breakthroughs, we can live a life that prioritizes activating longevity genes. This means activating our cells to “shift to survival mode” but not enough to cause havoc to the system.


Although movement itself has positive effects, HIIT (high intensity interval training) workouts seem to “engage the greatest number of health-promoting genes.”

You’ll know you are doing vigorous activity when it feels challenging. Your breathing should be deep and rapid at 70 to 85 percent of your maximum heart rate. You should sweat and be unable to say more than a few words without pausing or breath. This is the hypoxic response, and it’s great for inducing just enough stress to activate your body’s defenses against aging without doing permanent harm.

Eat Less Often & Intermittent Fasting

Not malnutrition. Not starvation. These are not pathways to more years, let alone better years. But fasting–allowing our bodies to exist in a state of want, more often than most of us allow in our privileged world of plenty–is unquestionably good for our health and longevity.

Today, human studies are confirming that once-in-a-while calorie restriction can have tremendous health results, even if the times of fasting are quite transient.

Eat More Plants

Study after study has demonstrated that heavily animal-based diets are associated with high cardiovascular morality and cancer risk.

…if you’re interested in a long and healthy life, your diet probably needs to look a lot more like a rabbit’s lunch than a lion’s dinner. When we substitute animal protein with more plant protein, studies have shown, all-cause mortality falls significantly.

Plant-protein gives us “limited amounts of amino acids” and that’s good.

From a vitality perspective…a body that is in short supply of amino acids overall, or any single amino acid for a spell, is a body under the very sort of stress that engages our survival circuits.

Limiting the intake of amino acids inhibits an enzyme know as mTOR. Inhibiting mTOR means “cells spend less energy dividing and more energy in the process of autophagy, which recycles damaged and misfiled proteins.” Think of it as cell housekeeping.

The Environment

Don’t smoke. The air we breathe matters, and watch out for ways you’re exposed to radiation. Exposing our bodies to uncomfortable temperatures, such as taking a brisk walk in the cold for example, activates brown fat.

All of these habits help, but the fact of the matter remains: “The natural and necessary act of replicating DNA causes DNA breaks, trillions of them throughout your body every day.” To push humans to live even longer and more vibrant lives, we will rely on advances in healthcare, specifically, cellular reprograming.

I predict that cellular reprograming in the body will first be used to treat age-related diseases in the eye, such as glaucoma, and macular degeneration…But if the therapy is safe enough to deliver into the entire body–as the long-term mouse studies in my lab suggest they might one day be–this may be in our future.

Our Thoughts

Why Read the Book

This summary is not a call to forgo reading “Lifespan: Why We Age — And Whey We Don’t Have To“. We just think the book has so much to offer and this snapshot encourages you to read further.

  • Knowing the future of healthcare and wellness helps you make informed medical and life choices.
  • Gain a better understanding of how your body ages so you can take measures to live a vibrant and longer life. 
  • As scientists find ways to extend our lifetime, this has implications on how we live and plan our lives.
  • Celebrate the medical breakthroughs, from labs to human examples that steer the future of healthcare.

Most of the time, conversations on aging in popular culture focus on the external and optics: the skin, hair, our looks in general. But the aging process starts from within. Serums may allow us to “age gracefully”, but deteriorating eyesight, muscle, cognitive ability, these symptoms of aging, the ones that directly kill us, we often overlook.

This book reminds us that the most beautiful things are invisible to the naked eye. And that the most sacred parts of our bodies, can’t be gleaned through a mirror, but through a microscope.

About the Author

David Sinclair is a Biologist and Professor of Genetics and co-Director of the Paul F. Glenn Center for the Biology of Aging at Harvard Medical School

Commit to living.