Lillian Wilson

Defy Aging by Beth Bennett

Discover the causes and effects of ageing as well as various healthspan-prolonging solutions with the book ‘Defy Ageing.’

Defy Aging

Ageing is not merely a number but a dynamic biological process that influences our health, well-being, and societal structure. With an estimated 2 billion people aged 60 and above by 2050, addressing the challenges posed by ageing has become a pressing concern for individuals, communities, and healthcare systems alike.

In the midst of this evolving landscape, ‘Defy Ageing,’ a book by the esteemed geneticist Beth Bennett, emerges as a beacon of knowledge and hope. In this review, we will explore the book’s strengths, key takeaways, and how it offers a valuable resource for readers seeking to navigate the journey of ageing with wisdom and vitality.

Author’s background

Beth Bennett is a highly accomplished PhD geneticist with expertise in evolutionary genetics and the science of ageing.

Beth Bennett (r)

With over fifty publications in peer-reviewed journals, she has made significant contributions to the field of biology. For three decades, she shared her knowledge and passion as a college biology professor at the University of Colorado in Boulder. Presently, she hosts a science-focused radio show and maintains a blog dedicated to various aspects of ageing. Her extensive experience and dedication to scientific research make her a prominent figure in the study of ageing.

What is the book about?

‘Defy Ageing’ aims to provide readers with a deeper understanding of the ageing process and explore novel research on interventions to mitigate its effects. The book begins with an explanation of the biology of ageing, emphasising that ageing is a normal process experienced by all individuals rather than a disease.

In the initial chapters, the book delves into the history and theories surrounding ageing. These theories serve as a basis for understanding ageing’s intricacies and the potential strategies to combat it.

Chapter 3 covers the ‘how’ behind ageing, introducing the mechanisms that underlie ageing. Chapters 4 to 8 are devoted to exploring individual body systems, beginning with the skin, muscle, bone, cardiovascular, and nervous systems.

In the final two chapters, the author introduces the concept of interventions – actions, drugs, and compounds – that hold promise in slowing down or even reversing certain age-related events. While some ideas may be more speculative than others, they are all supported by experimental evidence, including human trials and animal studies.

Table of contents

  • 1. What Is Aging, and Why Do We Get Old?
  • 2. The Why of Aging, or Evolutionary Explanations for Why We Grow Old
  • 3. The How of Aging
  • 4. Skin
  • 5. Muscles
  • 6. Skeleton
  • 7. Cardiovascular System
  • 8. The Brain and Cognitive Decline
  • 9. Interventions Part 1: Actions You Can Take
  • 10. Interventions Part 2: Drugs and Supplements You Can Take
  • Notes
  • Bibliography.
  • About the Author

Key takeaways from ‘Defy Ageing’

1Embracing intermittent living can enhance healthspan

In ‘Defy Ageing,’ the concept of intermittent living is explored, drawing inspiration from our ancestors’ evolutionary background. Our hunter-gatherer forebears faced various challenges like cold exposure, heat and periodic food scarcity that triggered internal repair systems.

Modern research indicates that combining cold exposure, heat, and fasting, can lead to improved metabolic markers like body weight, insulin levels, blood glucose, and various lipids, including cholesterol. This combination, referred to as intermittent living, aims to mimic the lifestyle of our ancestors and could serve as a ‘vaccine’ of sorts, encouraging our cells to develop protective mechanisms against contemporary lifestyle challenges.

2Heat and cold exposure brim with health benefits

‘Defy Ageing’ suggests that brief exposure to temperature extremes like heat and cold can activate defence mechanisms in our cells, leading to better health outcomes.

Studies have long demonstrated the positive effects of temperature extremes on longevity and stress resistance. For instance, people who used a sauna frequently showed significantly reduced risks of various heart diseases and lower all-cause mortality rates.

On the other hand, cold exposure has been shown to reduce inflammatory compounds and stress hormones while inducing changes in blood chemistry.

3Caloric Restriction has the capacity to extend both healthspan and lifespan

Caloric Restriction (CR) has been extensively studied and proven to have a significant potential for extending both healthspan and lifespan in various animal models. By reducing calorie intake without causing malnutrition, CR activates protective mechanisms within cells, leading to enhanced overall health and a longer, more vibrant life. Animal studies have shown that CR can extend life span by up to 300%, and the subjects remained in better health for much of that extended period. Long-term studies in primates, including monkeys, have demonstrated that CR not only increases longevity but also effectively prevents or delays the onset of chronic diseases, such as diabetes, cardiovascular issues, neurodegenerative disorders, and autoimmune conditions.

Furthermore, CR has been associated with improvements in important health indicators, including reduced oxidative stress, enhanced mitochondrial activity, better cholesterol levels, blood pressure regulation, and reduced inflammation. Along with these benefits, CR has also shown promise in improving bone health, brain function, arthritis management, diabetes control, and lowering the risk of cancer.

Overall rating & strengths and weaknesses, according to readers’ reviews

The book has gotten 4.62 ⭐️ on GoodReads.


  • Presents an unbiased evaluation of ageing research.

  • Comprehensive and up-to-date.

  • Offers useful tips, advice, and long-term planning tools.

  • The level of depth in the main text is suitable for non-scientists to follow, with ample notes and citations for further exploration.

  • The inclusion of lists of acronyms at the end of each chapter facilitates easy reference and comprehension while reading.


  • The book does not present any revolutionary approaches to ageing and health. Nevertheless, it will be an informative read for people unfamiliar with the subject, as it summarises common theories about health and longevity.

Best quotes from ‘Defy Ageing’

“Some evidence indicates that cold exposure, like sitting in an ice bath (which sounds worse than a sauna), can have beneficial effects. These include reducing inflammatory compounds and stress hormones, and changes in blood chemistry.”

“Cortisol, in particular, is released by emotional stresses. Some of its effects include breaking down muscle tissue (to generate energy for an anticipated emergency) and contributing to stomach ulcers (by increasing the formation of stomach acids). Maybe worst, high and sustained levels of cortisol reduce the ability of our brains to adapt and learn from new situations, and to store the memory of how to do that.”

“But for various, many poorly understood reasons, such as oxidation damage, the immune response that produces inflammation can become stuck in the on position as we get older. Then, the hallmarks of constant inflammation, increased blood flow and immune cell activity, can cause their own damage.”

Final takeaway

‘Defy Ageing’ by Beth Bennett is a well-written and comprehensive synthesis of scientific disciplines related to ageing. It offers valuable insights into the biology of ageing, exploring potential interventions to mitigate its effects.

If you are new to the topic of longevity and ageing, ‘Defy Ageing’ will be an excellent choice that will provide you with basic knowledge and enable further exploration of the subject.

Where to buy

You may purchase ‘Defy Ageing’ on Amazon at the best price. It is available in hardcover and Kindle versions, so you may choose an option that appeals to you the most.

Healthypedia FAQ

The book does not present revolutionary approaches to ageing, but it summarises common theories about health and longevity, making it an informative read for those unfamiliar with the subject.

Exposures to heat, such as regular sauna use, have been linked to reduced risk of heart disease, dementia, and improved blood pressure. On the other hand, cold exposure can reduce inflammation and stress hormones, improving the immune system's response to infection and inflammation.

Intermittent living, inspired by our ancestors' lifestyle, combines exposure to temperature extremes like cold and heat with occasional fasting. This approach triggers internal repair systems, leading to improved metabolic markers and better overall health.

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