Upton Sinclair and the Radical Power of Fasting

Upton Sinclair lived from 1878 to 1968 and began experimenting with fasting to treat his own chronic health problems—likely around 1910 or 1911, based on his writing. When you hear the name Upton Sinclair, you might picture the muckraking journalist who exposed the horrors of the American meat industry in The Jungle (1906). But Sinclair’s career extended far beyond social reform. He was also a dedicated experimenter in health and longevity—and one of the most vocal public advocates for fasting in the early 20th century.

In fact, Sinclair once claimed: “Fasting is the greatest remedy—the physician within.”

Let’s explore how this controversial author became a champion of fasting, what he practised and preached, and why his legacy still matters today for anyone interested in self-healing and health freedom.

A Writer Turned Wellness Crusader

Upton Sinclair wasn’t a doctor or a scientist—but he was a prolific writer with a relentless curiosity. Around the 1910s, plagued by chronic health issues like headaches, fatigue and digestive problems, he began to explore alternative health methods. That led him to fasting.

His personal experiments with multi-day fasts yielded what he described as dramatic improvements in health and mental clarity. He became so convinced of its power that he wrote a short book in 1911 called “The Fasting Cure.”

The Fasting Cure: Sinclair’s Bold Claims

Sinclair’s book was not subtle. He claimed fasting could prevent and cure almost every disease under the sun—from asthma and arthritis to cancer and syphilis. While these claims went far beyond what science (then or now) could verify, the book struck a chord with the American public—especially during a time when patent medicines and dubious cures were common.

Some of his core ideas included:

• Fasting unlocks the body’s natural healing power.

• Doctors often prolong illness by prescribing food.

• Most chronic illness is a result of overfeeding and improper digestion.

He cited not just his own experience, but also those of friends and hundreds of readers who wrote to him with fasting success stories.

Sinclair’s Method

Sinclair advocated longer fasts—sometimes up to 10 days or more—under self-supervision. He usually fasted on water alone, and recommended breaking the fast very carefully with raw fruits or broths. He was influenced by the early Natural Hygiene movement (which also inspired Herbert Shelton later on), and was wary of mainstream medicine.

His basic formula:
When sick — stop eating. Let the body heal. Then nourish it well.

It’s important to note: Sinclair’s fasts were extreme by today’s standards. He didn’t always approach them with modern safety protocols. For someone with underlying health conditions, this could be risky—especially without guidance. But for Sinclair, the results were worth it.

Criticism and Controversy

Mainstream doctors of the time dismissed Sinclair’s book as dangerous quackery. And indeed, not every follower had positive outcomes—some misapplied fasting or went too far. But the backlash often ignored Sinclair’s central, common-sense point: that the body is capable of healing, and sometimes less is more when it comes to food.

Today, much of what he suggested is supported by research into autophagy, insulin resistance, and metabolic health. Intermittent fasting, once fringe, is now practically mainstream. Sinclair was clearly ahead of his time.

A Legacy of Radical Simplicity

What makes Upton Sinclair so fascinating isn’t just that he fasted—it’s why he fasted. He believed that industrial society had become toxic: in its food, its medicine, and its thinking. He saw fasting as a revolutionary act—a way to reclaim control over the body and escape from both corporate and medical dependence.

For those of us interested in budget health, anti-aging, and natural healing, Sinclair’s ideas feel surprisingly modern. He wasn’t selling supplements, nor meal plans—he was offering something profoundly cheap and powerful:

Do nothing. Eat nothing. Let the body work.

Final Thoughts

Upton Sinclair’s The Fasting Cure might read like a relic from another age, but it’s part of the foundation of today’s fasting movement. His willingness to experiment, document, and defy medical norms laid the groundwork for people like Herbert Shelton, Valter Longo, and Jason Fung to challenge the status quo.

If you're exploring fasting for health or chronic disease, it’s worth reading Sinclair—not as a scientific guide, but as a spark to help think differently about food, illness, and the incredible intelligence of the body.

Further Reading:

• “The Fasting Cure” by Upton Sinclair

  • Upton Sinclair was not only a prolifc and much admired author, but also a follower of Bernarr MacFadden's Physical Culture movement (see his Physical Culture Cook Book, 1901) and a member of the editorial staff of Physical Culture Magazine. Dedicated to MacFadden, this volume advocates the benefits of systematic fasting in producing long-lasting health benefits. This book is a reprint of two articles written by Mr. Sinclair for the Cosmopolitan Magazine on the general subject of fasting for health, as well as many testimonies from letter he received from people who tried fasting with fantastic results including results such as cures for a great number of diseases and ailments including cancer. Mr Sinclair gives general outlines for fasting but at least that every person is biologically a little different and result vary from one person to the next. Almost all results in the book are positive and the negative results seems to be from people who did not fast correctly or came off the fast incorrectly.

• Herbert Shelton’s “Fasting Can Save Your Life”

  • Herbert M. Shelton outlined his theory that fasting is a key component in promoting healing. The book's ideas run counter to the well-known conventional wisdom that those who are sick must eat to "keep up their strength" and posits that fasting is a natural part of the rhythm of life. Shelton's book outlines the history of this practice and explains the following in detail: what is fasting, the purpose of fasting, how to fast successfully, intermittent fasting for healing, and the benefits of fasting in general.

• Modern fasting research: Jason Fung’s The Complete Guide to Fasting

  • The ultimate resource on intermittent fasting, the incredibly effective therapeutic approach to feeling better and losing weight that produces life-changing results.
    Whether you’re new to intermittent fasting or you want to fine-tune your fasting plan, this is the intermittent fasting manual to help you build the right fasting program for the best results. Whether your goal is to lose weight, improve your body’s insulin response, sharpen your mental faculties, turn down depression or anxiety, or slow the aging process, The Complete Guide to Fasting is the best companion for your journey.