On HCG Diet Dangers

First published 8 May 2015 · revised August 2026 with the current regulatory status and eleven more years of evidence on very-low-calorie dieting.

I have had patients ask me about the HCG diet for well over a decade now, and every few years it resurfaces under a new brand name with the same promises attached. It never really goes away.

A few years ago, a former residency colleague called to ask my advice about a practice opportunity: one of the HCG diet companies had offered him a lucrative position, needing a physician’s name and license to lend their weight-loss program more credibility. Among the benefits on offer was a promise to have him driving a Mercedes-Benz before the year was out. That offer alone tells you plenty about the business model, before we even get to the biology.

The HCG weight-loss craze is really just the most recent entry in a long line of diet fads — Atkins, Hoodia, acai berry, and now homeopathic HCG. What is on offer is always the same promise: a shortcut past the slow, unglamorous work of eating less and moving more.

What Is HCG?

HCG — human chorionic gonadotropin — is a hormone naturally produced during pregnancy. It is what turns a urine pregnancy test positive soon after conception, first made by the embryo and later in large amounts by the placenta. Early on, it sustains progesterone secretion from the corpus luteum, the structure left behind in the ovary after ovulation, which prepares the uterus for implantation. Later in pregnancy it appears to help shelter the fetus from the mother’s immune system, and there is evidence it plays a role in tissue growth.

HCG is structurally similar to LH, a pituitary hormone present in both sexes that triggers ovulation in women and stimulates testosterone production in men. Because of that similarity, and because HCG is straightforward to extract and purify, it is used clinically in fertility treatment — always by injection.

The detail that matters for everything below: HCG is a glycoprotein, a two-chain molecule of roughly 237 amino acids built from an alpha subunit shared with three other pituitary hormones and a unique beta subunit, the whole thing heavily coated in sugar groups.²

What Is the HCG Diet?

The diet plan sold alongside the HCG product is a very low calorie diet, typically around 500 calories a day, against an average adult requirement of roughly 1,600–2,000 calories. The old rule of thumb — that a 3,500-calorie deficit equals a pound of fat lost — is a rough approximation at best; real weight loss slows as the body adapts, which is part of why the early, dramatic numbers on this diet look so impressive and predict so little about what happens next (more on that below). But even allowing for that, a 500-calorie diet is a severe deficit, and it is where essentially all of the weight loss on this plan comes from.

For most people who try it, that rapid early drop is the entire attraction. After all, the sooner the weight is gone, the better — or so it seems. Later, in what is usually called a maintenance phase, calories are increased toward something closer to a normal diet.

Is There Any Scientific Evidence HCG Causes Weight Loss?

No. The most direct answer comes from a 1995 criteria-based meta-analysis of every placebo-controlled trial of HCG for obesity then available. It found no evidence that HCG produced additional weight loss, fat redistribution, appetite suppression, or improved well-being beyond what calorie restriction alone achieved — and the methodologically stronger trials in the pool were consistently the most negative.¹ No trial since has overturned that finding.

The biology explains why. As a glycoprotein of roughly 237 amino acids, HCG cannot survive the gut intact. Like any other protein in your dinner, it is broken down by stomach acid and then by intestinal enzymes into individual amino acids and sugar molecules — the “pieces” that actually get absorbed, not the intact, functional hormone. This is precisely why fertility treatment with HCG is given by injection rather than by mouth. Sprays and sublingual drops fare no better: HCG is simply too large a molecule to cross skin or mucosal barriers intact in any meaningful amount.

Even the injectable route, which does get intact HCG into the bloodstream, has not been shown to add weight loss independent of the very-low-calorie diet it is paired with in the same trials.¹

All of the weight loss in an HCG diet plan is caused by the very low calorie diet. HCG is the trick that gets you to pay for the privilege of semi-starving yourself on 500 calories a day.

What has changed since 2015

The regulatory picture, if anything, has only hardened. The FDA and FTC jointly warned seven companies in December 2011 that homeopathic HCG products were being sold illegally, with no FDA approval and no supporting evidence.³ The FTC followed with continued enforcement — a $1 million settlement with HCG Diet Direct in 2014 over claims that its drops caused rapid, substantial weight loss.⁴ And this is not a settled fight from a decade ago: as recently as February 2025, the FDA was still publicly warning consumers away from these products.

Two other things I did not have solid numbers for in 2015:

The gallstone risk is now measured, not just observed. A matched cohort study of nearly 5,000 people across 28 Swedish weight-loss centers found roughly three times the rate of gallstones requiring hospital care or surgery on a 500-calorie diet compared with a standard 1,200–1,500-calorie diet — 48 cases against 14 over one year.⁶

The metabolic slowdown outlasts the diet by years, not weeks. The clearest data on this comes from an unrelated but comparably extreme intervention: contestants on The Biggest Loser, followed six years after their televised weight-loss competition. Despite regaining most of the weight, their resting metabolic rate remained substantially suppressed — a persistent metabolic adaptation that did not resolve when the weight came back.⁷ I have no reason to think a 500-calorie HCG diet is gentler on the body's metabolic machinery than that program was.

HCG Diet Dangers

There are several concrete reasons for concern with this diet plan:

• Very low calorie diets are unhealthy. It is practically impossible to meet nutritional needs on fewer than 800 calories a day, and malnutrition — vitamin and essential nutrient deficiency — is a real risk. Vitamin and mineral supplements, often recommended alongside these plans, help but are not a substitute for an adequate diet. The FDA's 2025 warning specifically flags electrolyte imbalance and irregular heartbeat as risks of the 500-calorie plan.
• Very low calorie diets cause gallstones. I have seen this firsthand in patients on aggressive diets, and the Swedish cohort data now puts a number on it: roughly three times the risk compared with a standard low-calorie diet.⁶ Gallstone surgery is no small thing, even done laparoscopically.
• HCG diets slow metabolism. A severe, rapid deficit pushes the body into a defensive, energy-conserving state, and the best long-term data available on comparably extreme weight loss shows that slowdown can persist for years.⁷
• HCG diets are not sustainable. These plans are aggressive enough that they are difficult to follow even short-term. What I have seen, over and over, is a patient getting excited about the HCG diet, pushing through several weeks of near-starvation, losing weight in the double digits and telling everyone about it — including me — and then sliding back, gradually or all at once, into their old habits. Often, by their next appointment, they have regained everything and then some. That yo-yo pattern is not healthy for the body, and these patients would frequently have been better off not dieting this way at all.
• HCG diets are expensive. Wasting money on a diet fad is not news, but it still stings when it happens to you — and the FTC's $1 million judgment against just one HCG marketer gives some sense of how much money has moved through this industry.⁴

Concluding Thoughts

One thing that has always puzzled me about the HCG weight-loss craze is why people do not apply their own common sense to it. Women gain weight during pregnancy — some more than 30 lbs. If HCG, the hallmark hormone of pregnancy, had any direct effect on body weight, the more plausible direction would be weight gain, not loss. That is an illustration, not a proof, but it is worth sitting with before crediting the hormone with anything.

I hope what I have written here helps some readers use that same common sense to avoid wasting money and risking their health on this particular fad. If I could have another wish, I would wish the HCG diet would simply go away — but wishes like that are rarely granted. I will settle instead for watching it keep fading into the background noise of diet plans that work for a while and disappoint later, the way so many fads before it have. You made it to the end of this article, which tells me you were probably already looking for something better. Good.