The HCG diet — why it never worked and what the research actually says
4 min read · Uplevel editorial
In 1954, a British physician named Albert T.W. Simeons published a paper in The Lancet titled "The Action of Chorionic Gonadotrophin in the Obese." He had been working in Rome, treating patients with obesity, and he had developed a theory. The theory was this: HCG, the hormone present in high concentrations during pregnancy, had a special property — it mobilized fat stored in "abnormal deposits," the kind of stubborn fat that collects around the hips, thighs, and abdomen in ways that conventional dieting failed to touch. Combine HCG injections with a 500-calorie-per-day diet, Simeons argued, and you would lose fat from those deposits specifically, while sparing muscle, without the hunger that would normally make a 500-calorie diet intolerable. The weight would come off in the right places. The hunger would be manageable. The results would be dramatic and lasting.
The theory was elegant, the clinical anecdotes compelling, and the mechanism almost entirely fabricated.
Simeons spent the following decades running his protocol at a clinic in Rome, charging considerable fees, treating patients from around the world, and building a loyal following that has persisted, with periodic revivals, into the present day. His 1967 book, "Pounds and Inches," remains in print and in circulation online. The HCG diet has been rediscovered roughly every decade since, adapted for various eras — injections in the sixties and seventies, oral drops in the nineties and two-thousands, "homeopathic" HCG sprays and sublingual tablets in the 2010s. Each revival has brought with it enthusiastic testimonials and the same essential claim: HCG does something that makes the extreme calorie restriction work differently than it would without the hormone.
The controlled trials don't support it. Not some of them. All of them.
The first rigorous test came in the 1970s, when researchers at several institutions ran double-blind, placebo-controlled trials of the Simeons protocol. In a double-blind trial, neither the patient nor the treating provider knows who is receiving HCG and who is receiving a placebo injection. When you introduce that design — the design that exists specifically to separate what patients believe is happening from what is actually happening — HCG stops working. Patients in the placebo arm lost the same amount of weight as patients in the HCG arm. They reported the same levels of hunger. They showed the same changes in body composition. The HCG injection, in controlled conditions, did nothing that the placebo injection didn't also do.
The conclusion those researchers reached was precisely what you would predict from basic physiology: the weight loss in the Simeons protocol comes from eating 500 calories a day. That's it. A 500-calorie diet produces severe caloric restriction. Severe caloric restriction produces weight loss. The mechanism is arithmetic, not endocrinology.
The hunger suppression Simeons described — that profound reduction in appetite that his patients reported while on HCG injections — is also fully explicable without the HCG. Extreme caloric restriction, especially combined with significant protein intake (the Simeons protocol allowed certain lean proteins), can after the first few days produce a ketosis-adjacent metabolic state that meaningfully reduces hunger signals. The adaptation to near-starvation includes hormonal shifts — lower insulin, elevated glucagon, increasing ketone production — that genuinely do reduce appetite. The body, when sufficiently starved, stops sending as many hunger signals because the hunger signals have failed repeatedly to produce food. None of this requires HCG. The HCG was, in all likelihood, functioning as an elaborate placebo that helped patients commit to a diet they might otherwise have abandoned.
The placebo hypothesis is, in its way, generous. It suggests that HCG at least produced compliance. The ritualized injections, the clinical protocol, the promise of a mechanism — all of it may have provided the psychological scaffolding for adhering to a diet that was, frankly, medically dangerous and nearly impossible to sustain through willpower alone. If that's true, the HCG diet "works" in the same sense that any extreme calorie restriction enforced through ritual commitment works. Temporarily.
The FDA weighed in formally in 1975, requiring labeling on HCG products that specified the drug was not approved for weight loss and was not demonstrated to be effective for that purpose. The label was required, but the diet continued. It has a particular resilience, the HCG diet — a quality shared by most weight-loss protocols that produce rapid results for a predictable reason (dramatic calorie restriction) while offering a more appealing narrative explanation (special fat-burning action of the hormone). The rapid initial results are real. The narrative is not.
The FDA took stronger action in 2011, specifically targeting homeopathic HCG products — the drops, sprays, and sublingual tablets that had proliferated as alternatives to prescription injections. These products typically contain no measurable HCG at all; they're diluted past the point of pharmacological relevance by the conventions of homeopathic preparation. The FDA issued warning letters to multiple companies, stating that these products were being marketed illegally and that they were neither safe nor effective for weight loss. Several companies ceased selling them following those letters. Others did not, and the products remain available online through various channels where enforcement is difficult.
The homeopathic version of the HCG diet is worth dwelling on for a moment because it makes the underlying dynamic unusually visible. If a product containing no HCG whatsoever produces results indistinguishable from a product containing pharmaceutical-grade HCG — which the controlled trials suggest would be the case — then the only thing the product is actually delivering is the ritual and the belief — the placebo stripped of even the pretense of an active ingredient. What that leaves is the 500-calorie diet, doing all of the work and carrying all of the risk: the documented fatigue, electrolyte disturbances, gallstones, and cardiac arrhythmia that come with that degree of restriction. The honest reading of the HCG diet is that the hormone was never the active ingredient — the deprivation was, and any serious conversation about losing weight safely belongs with a provider who can account for that risk rather than disguise it behind an injection.
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