Why Fasting Is Free and That's the Problem

Upton Sinclair spent roughly $15,000 over six to eight years chasing a cure for chronic nervousness, headaches, and insomnia — physicians, surgeons, druggists, sanatoriums, one specialist after another. Then he stopped eating for twelve days and got better than any of it had managed. His conclusion, published in 1911's The Fasting Cure, was blunt: the reason fasting wasn't being recommended to him had nothing to do with whether it worked.

It's a provocative claim, and it's worth taking seriously — not because Sinclair was a scientist, but because the pattern he described is one of the more testable ideas in his book.

The Argument, In Sinclair's Own Terms

Sinclair's logic ran like this: a treatment that costs nothing, requires no prescription, and can be self-administered at home generates no revenue for anyone. Physicians who built their practices around ongoing visits, tonics, and surgical referrals had no structural incentive to investigate a method that put them out of a job for the duration of a patient's fast. He wasn't accusing individual doctors of bad faith — he was describing an incentive structure, and arguing that incentive structures shape what gets recommended regardless of anyone's intentions.

He backed this with a number that struck him as damning. After he published an article about his experience in Cosmopolitan magazine, he received somewhere between 600 and 800 letters from readers who had tried fasting themselves. Of those, he counted barely two from physicians. Of 109 respondents he tallied in detail, 100 reported clear benefit. Sinclair found it telling that almost none of this evidence was coming from within the medical system that was supposed to be evaluating it.

The Stethoscope Comparison

Sinclair reached for a historical parallel to make his case less about fasting specifically and more about how institutions treat threats to established practice. He cited Dr. Elliotson, a nineteenth-century physician who championed the stethoscope — a device now considered basic medical equipment. In its early years, the stethoscope was mocked and its advocates marginalized; Elliotson was effectively pushed out of professional medicine for promoting it. Within a generation, no doctor practiced without one.

Sinclair's point wasn't that fasting and the stethoscope are medically equivalent. It was narrower: that professional resistance to a new idea tells you almost nothing about whether the idea is correct, and quite a lot about who stands to lose from adopting it.

What Was Actually Free About Fasting

It's worth being precise about what Sinclair meant, because "free" undersells the contrast he was drawing. His illness had been managed through an expensive, ongoing relationship with the medical establishment — recurring appointments, changing prescriptions, dietary programs that required supervision. Fasting required none of that. Once a person understood the basic principles (which Sinclair spent much of his book laying out), it could be done without a professional in the room at all.

He wrote of one correspondent who put it starkly: they'd spent over $500 on medicines with no lasting result, and thirty cents on lemons and water during a fast produced relief they described as immeasurably more valuable. Whether that number is literally accurate is beside the point Sinclair was making — the structure of the comparison, expensive ongoing treatment versus a method that costs almost nothing, was the argument.

Where the Argument Gets Complicated

Sinclair's framing was persuasive, but it wasn't the whole story, and it's worth being honest about where it thins out.

The medical objections of 1911 weren't purely financial self-interest dressed up as science. Doctors raised a real and, at the time, reasonable concern: fasting was being recommended on the basis of anecdote, not controlled study. There was no documented mechanism for why extended abstinence from food might heal chronic conditions rather than simply weaken the body further. That gap wasn't closed by Sinclair's case reports, however numerous — it was closed decades later by actual metabolic and cellular research.

It's also true that financial incentive doesn't fully explain medical caution even today. Fasting isn't appropriate for everyone. People with certain metabolic conditions, those on specific medications, and pregnant or nursing women need guidance that a free, unsupervised fast doesn't provide. Some of the caution Sinclair dismissed as self-interest was, in hindsight, appropriately conservative.

What Modern Science Eventually Confirmed

The mechanistic gap that 1911 medicine correctly identified has since been filled in substantially. Research on ketosis reframed it as a normal, functional metabolic state rather than a starvation symptom. Studies measuring human growth hormone found increases of 300–500% during a 24-hour fast, suggesting fasting is hormonally active rather than simply depriving. Yoshinori Ohsumi's Nobel Prize–winning work on autophagy in 2016 gave fasting a cellular mechanism that didn't exist in any textbook when Sinclair was writing. None of this required Sinclair's economic argument to be true — but it did vindicate his underlying observation that something real was happening, whatever the reason doctors weren't investigating it.

The Pattern Worth Remembering

Sinclair's specific accusation, that doctors ignored fasting purely to protect their income, is impossible to fully verify and was almost certainly too simple. But the broader pattern he pointed to — that institutions are slow to adopt interventions that don't fit their existing business model, even when patient evidence is accumulating — shows up again and again in the history of medicine, from the stethoscope to hand-washing to, more recently, the slow institutional embrace of time-restricted eating itself. Sinclair may have overstated the case in 1911. He wasn't wrong that the incentive structure mattered.

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Frequently Asked Questions

Did Upton Sinclair really believe doctors were hiding a cure? Not quite — his argument was about incentives, not conspiracy. He believed the medical profession had no financial reason to investigate or recommend a free, self-administered treatment, not that individual doctors were knowingly suppressing something they believed worked.

Was there any legitimate medical objection to fasting in 1911? Yes. The main fair criticism was that fasting's benefits were documented only through anecdote and case reports, with no controlled studies and no known biological mechanism. That gap was real and wasn't resolved until much later research on ketosis, hormones, and autophagy.

How many people wrote to Sinclair about their fasting experiences? He reported receiving 600–800 letters after his original magazine article, and of 109 he analyzed in detail, 100 reported clear benefit.

Is fasting actually free today? Fasting itself costs nothing beyond the food you're not buying, though many people now use apps, coaching, or community programs alongside it — which is a different question from whether the practice itself requires paid intervention.

Does modern medicine still resist fasting for the same reasons? Less so. Growing clinical research and mainstream recognition — including position statements from major health organizations — have shifted the landscape considerably since 1911, though individual physician awareness still varies.

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.

Sinclair, U. (1911). The Fasting Cure. Mitchell Kennerley.

Why Fasting Is Free and That's the Problem