Why Fasting Fell Out of Fashion (And Why It's Coming Back)

In 1911, fasting was a genuine grassroots health movement — thousands of ordinary people were trying it, swapping letters about their results, and treating it as a legitimate alternative to expensive medical care. A century later, most people had never heard of it as anything other than a religious practice. What happened in between, and why is fasting suddenly everywhere again?

A Popular Remedy, Then a Forgotten One

Upton Sinclair's 1911 book The Fasting Cure captured a moment when fasting was a genuine cultural phenomenon. His original magazine article on the topic generated somewhere between 600 and 800 letters from readers who had tried fasting themselves, and Sinclair collected 277 of those cases into his book as a kind of grassroots case series. People used fasting for rheumatism, headaches, insomnia, and digestive complaints, often after conventional treatments had failed them.

But this popularity ran directly against the interests of the medical establishment of the time. Sinclair was blunt about the conflict: doctors made their living prescribing drugs and procedures, and a treatment that cost nothing and required no professional supervision was a direct threat to that business model. He was publicly branded a "shallow and unscrupulous sensationalist" by the New York Times, and of the hundreds of letters he received describing fasting experiences, only two came from physicians.

The Institutional Backlash

The hostility wasn't just rhetorical. Sinclair documented the case of a man fasting in Seattle whose fast was forcibly interrupted by health officials who tried to have him declared insane; he died shortly afterward, and Sinclair argued it was the shock of the intervention — not the fasting itself — that killed him. Stories like this illustrate how far the medical establishment was willing to go to discourage a practice it couldn't control or profit from.

Fasting also had an image problem it never quite shook off. It got tangled up with extreme physical culture movements, unregulated sanatoriums, and figures like Dr. Linda Burfield Hazzard, whose fasting-based practice in Washington State became notorious. As 20th-century medicine professionalized around pharmaceuticals, lab tests, and insurance billing, a treatment with no product to sell and no way to measure compliance had no natural home in that system. It quietly slipped out of mainstream practice and became associated mostly with religious observance or fringe wellness culture.

What Changed

Fasting's return to relevance didn't come from a rediscovery of Sinclair's book — it came from decades of laboratory research into what actually happens inside the body when it goes without food. Modern science has given precise mechanisms to phenomena Sinclair could only describe anecdotally. Where he wrote about the body "clearing toxins" and directing energy toward healing during a fast, researchers now study autophagy — the cellular process where the body breaks down and recycles damaged components, a process shown to ramp up significantly during fasting states. Where Sinclair noted that hunger vanished after a few days and mental clarity improved, modern metabolic research has mapped the shift from glucose to ketone metabolism that produces exactly those effects.

The rise of intermittent fasting protocols like 16:8 and 5:2 also made the practice far more approachable. Sinclair's fasts ran to 12 days; most people today are fasting for 14–18 hours within a daily routine, which lowers the barrier to entry dramatically. Add smartphone apps, tracking tools, and a large body of peer-reviewed research into metabolic health, and fasting has re-entered mainstream conversation on far more credible footing than it had a century ago.

The Same Debate, New Terms

In some ways, the tension Sinclair described hasn't disappeared — it's just changed shape. Fasting is still a "free" intervention with no product to sell, and it still sits somewhat awkwardly alongside a healthcare and food industry built around consumption. But it now has something Sinclair's era lacked: a substantial and growing body of clinical research from major medical journals, giving it credibility that anecdote alone never could.

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FAQ

Did doctors always oppose fasting? Not universally, but organized medicine in Sinclair's era was broadly hostile — he noted that of hundreds of reader letters describing fasting results, only two came from physicians.

Is fasting today the same as what Sinclair described? The core idea — abstaining from food to let the body rest and repair — is the same, but modern protocols are far shorter and more structured, and are backed by clinical research rather than anecdote alone.

Why did fasting become associated with fringe wellness culture? Because it had no natural place in a 20th-century medical system built around pharmaceuticals and billable procedures, it drifted toward physical culture and alternative health movements instead of mainstream medicine.

What brought fasting back into the mainstream? Decades of research into autophagy, metabolic switching, and insulin sensitivity gave scientific grounding to effects that were previously only described anecdotally.

Is fasting recommended by doctors now? Many physicians and dietitians now discuss intermittent fasting as one legitimate option among several for metabolic health, though it isn't right for everyone and should be discussed with a healthcare provider.

This article draws on historical research from 1911 and is for informational purposes only — not medical advice. Always consult a qualified healthcare professional before making any dietary changes.

Why Fasting Fell Out of Fashion (And Why It's Coming Back)