HCG Diet Phase Calendar: Simeons Protocol & Why It Doesn’t Work

✓ Medically reviewed by  ·  Last reviewed: May 2026

Morgan Ellis

Pharmacy Researcher · 8 years experience

Pharmacy researcher with 8 years reviewing clinical drug information, generic formulation equivalence, and international pharmaceutical standards. Focuses on patient-facing accuracy in medication education.

Where the HCG Diet Came From

A.T.W. Simeons was a British endocrinologist working in Rome in the 1950s. He observed that pregnant women who experienced famine during World War II preferentially mobilised “abnormal fat” while preserving muscle — and hypothesised that HCG, the hormone of pregnancy, was the mediator. His 1954 manuscript “Pounds and Inches: A New Approach to Obesity” set out a protocol pairing daily HCG injections with severe caloric restriction. The protocol became fashionable in obesity clinics in the 1960s, fell out of clinical favour by the 1980s, and re-entered popular culture in 2007 via Kevin Trudeau’s bestseller “The Weight Loss Cure ‘They’ Don’t Want You to Know About”.

The Simeons hypothesis is testable. Simeons himself reported that HCG mobilised “abnormal fat” while sparing structural fat and muscle. Subsequent randomised trials — Bosch et al. 1990, Lijesen et al. 1995 (a meta-analysis of 14 controlled trials), Greenway and Bray 1977 — showed no difference between HCG and saline placebo for any of these claims. The weight loss tracked the caloric restriction, not the hormone.

The Original Simeons Phase Calendar

The protocol has four phases. Day numbers below reflect the original 26-day version; the longer 43-day version uses 40 VLCD days.

Phase 1 — Loading (Days 1–2)

On day 1 the user begins HCG injections (Simeons specified 125 IU/day intramuscularly) and is instructed to eat as much as possible — “to load” — for two days. The rationale was to fill up “structural” fat reserves before the very-low-calorie diet (VLCD) begins. There is no physiological basis for the loading phase; the hormone has not had time to produce any effect at the doses used, and the practical effect is simply two days of overeating.

Phase 2 — VLCD (Days 3–25 or 3–42)

This is the core of the protocol. The user continues daily HCG and follows a strict 500 kcal/day diet built from a list of “approved” foods:

• Breakfast: coffee or tea (any quantity), no sugar, very small amount of milk allowed.
• Lunch and dinner each: 100 g lean protein (chicken breast, white fish, lean veal — no salmon, no eel, no tuna in oil) + one approved vegetable (single type per meal) + one Melba toast or grissini + one small fruit (apple, orange, ½ grapefruit, or 6 strawberries).
• Fluids: 2 L water per day. No oils. No butter. Very limited seasonings.

This is approximately 500 kcal/day. It is at the bottom of what nutritional medicine considers safe, and is well below baseline metabolic requirements for any adult. It is also nutritionally incomplete — protein quantity is at the floor, micronutrient density is poor, and essential fatty acid intake is approximately zero. The Simeons protocol explicitly forbade vitamin or mineral supplementation on the theory that HCG would prevent deficiencies; this part of the theory is unsupported.

Phase 3 — Stabilisation (Days 26–47, or 43–63 in the long version)

HCG injections stop. Caloric intake increases gradually back to maintenance. Sugar and starch remain forbidden. The user weighs daily and is instructed that any 1-kg gain triggers a “steak day” — a 24-hour fast followed by one large steak in the evening. The stabilisation logic is that HCG has “reset” the hypothalamic weight setpoint and that the user must avoid disrupting it with carbohydrates. This is a hypothesis, not a clinical finding.

Phase 4 — Maintenance (lifelong)

The user gradually reintroduces sugar and starch while monitoring weight. Cycles can be repeated, with a 6-week minimum break between courses to avoid HCG-receptor desensitisation. Long-term Simeons-protocol users frequently cycle two to four times per year.

Phase Calendar at a Glance — 26-Day Version

The 43-day version simply extends Phase 2 to 40 VLCD days (instead of 23) for users who want to lose more weight in a single course.

What the Evidence Actually Shows

A 1977 study by Greenway and Bray (UCLA) is widely cited because the placebo arm lost slightly more weight than the HCG arm. A 1990 trial by Bosch and colleagues showed identical weight loss in HCG and placebo groups. The 2017 Cochrane Library and the 2024 NEJM Evidence review of obesity pharmacotherapy both omit HCG entirely from approved or evidence-based options.

The mechanism by which the diet produces weight loss is therefore caloric restriction, not the hormone. A 500 kcal/day diet, sustained for 23–40 days, produces a calorie deficit of ~1,500–2,000 kcal/day, which corresponds to about 4–6 kg of fat loss over a long protocol — consistent with reported HCG-diet results. No hormone is required to produce this outcome.

What HCG at 125 IU/day Actually Does

At 125 IU IM daily, plasma HCG levels rise modestly. The pharmacological consequences in a non-pregnant adult are:

• Mild Leydig-cell stimulation in men, producing a small increase in testosterone. Not relevant for weight regulation.
• Mild ovarian stimulation in women, producing a small increase in estradiol and progesterone. Also not relevant for weight regulation.
• No effect on adipocyte lipolysis at these doses. HCG does not bind adipocyte receptors at clinically relevant affinity.
• No effect on hypothalamic appetite centres at these doses. The “reduces hunger” claim — central to Simeons’ marketing — has not survived controlled testing.

A user reporting that HCG “kills hunger” on a 500-calorie diet is reporting the well-documented hypothalamic adaptation to severe caloric restriction (which does blunt hunger signalling within 5–10 days), not a hormone effect.

Risks of the 500-Calorie Phase

The Simeons VLCD is well below modern medical-VLCD safety floors:

• Gallstones — rapid weight loss precipitates cholesterol crystallisation; symptomatic gallstones occur in 10–25% of users on protracted VLCDs.
• Muscle loss — at 500 kcal/day with the protein flux Simeons specified, fat-free mass loss is documented despite the “HCG preserves muscle” claim. Lean-mass scans on HCG-diet completers show identical fat-free mass loss to control diets at the same caloric intake.
• Electrolyte imbalances — sodium, potassium, and magnesium losses can produce arrhythmias. Sudden cardiac deaths have been reported on extended VLCDs without medical supervision.
• Hair loss — telogen effluvium 8–12 weeks after the protocol is common.
• Nutritional deficiency — micronutrient and essential fatty acid deficiencies develop within weeks. The protocol’s prohibition on multivitamin supplementation makes this worse.
• Rebound weight gain — long-term follow-up studies show HCG-diet weight regain rates similar to or worse than other VLCDs once normal eating resumes.

Modern Alternatives for Patients Who Want Real Weight Loss

The pharmacology of weight management has changed enormously since Simeons. As of 2026 several drugs have produced 5–25% body-weight reduction in randomised trials:

• Semaglutide (Ozempic at 1–2 mg, Wegovy at 2.4 mg) — 12–16% mean weight loss at 68 weeks. See our Ozempic buying guide.
• Tirzepatide (Mounjaro/Zepbound) — ~22% mean weight loss at 72 weeks (SURMOUNT-1).
• Retatrutide (Phase 3) — ~24% mean weight loss at 48 weeks in Phase 2; research-grade peptide available internationally.
• Orlistat — 3–5% at 12 months; OTC; modest but well-tolerated.

None of these is HCG. Patients comparing pharmacology should compare what the molecule does in randomised data, not what marketing claims for it.

Where to Buy Real HCG (For Real Indications)

Frequently Asked Questions

Does HCG actually help you lose weight?

At the doses used in the Simeons protocol (125 IU/day), HCG produces no measurable weight-loss effect compared with placebo in randomised trials. Weight loss observed on the protocol is fully attributable to the 500-calorie diet. This conclusion has been replicated across 14 controlled trials in the Lijesen 1995 meta-analysis and has not been overturned by subsequent research.

Why do users report dramatic weight loss on the HCG diet?

A 500-calorie/day diet sustained for 3–6 weeks reliably produces 4–8 kg of weight loss in adults with overweight or obesity — entirely from the calorie deficit. Severe caloric restriction also reduces hunger signalling within 5–10 days as a normal hypothalamic adaptation; users frequently attribute this to the hormone.

Is the HCG diet safe?

The 500 kcal/day phase is below modern medical-VLCD safety floors. Documented complications include gallstones, electrolyte imbalances, telogen-effluvium hair loss, and muscle loss. The protocol is not appropriate for individuals with cardiac disease, eating-disorder history, type 1 diabetes, or pregnancy. Anyone considering it should consult their physician — particularly because severe VLCDs without medical supervision have been associated with sudden cardiac events.

Are sublingual HCG drops effective for the diet?

No — they were never effective for any indication. HCG is a 36.7 kDa glycoprotein that cannot be absorbed sublingually in clinically meaningful amounts. Most “homeopathic HCG drops” sold over the counter contain no measurable HCG. See our deep-dive at HCG injections vs drops.

What’s the difference between the 26-day and 43-day Simeons protocols?

The 26-day version has 23 VLCD days; the 43-day version has 40 VLCD days. Phase 1 (loading) and Phase 3 (stabilisation) are unchanged. The longer protocol simply produces a larger total caloric deficit and therefore more weight loss. Risk of complications scales with duration.

What about the 800-calorie “modified Simeons” protocol?

Some practitioners use 800 kcal/day instead of 500 kcal/day, claiming better tolerability with similar weight loss. Tolerability is indeed better at 800 kcal/day, but the same conclusion applies: HCG itself contributes nothing beyond placebo. The weight loss tracks the calorie deficit.

Can I do the HCG diet without HCG?

Yes. A 500–800 kcal/day VLCD with appropriate medical supervision, multivitamin supplementation, and protein adequacy will produce the same weight loss the HCG-diet protocol produces. The Optifast and Cambridge Diet medical VLCD programmes have decades of clinical data and produce weight-loss outcomes similar to or better than the Simeons protocol — without the unsupported hormone.

If I want HCG for fertility or TRT, can I use it without doing the diet?

Yes — and this is the only context where HCG has clinical evidence. For fertility, TRT-adjunct, or PCT use see our HCG buying guide, dose protocol guide, and PCT protocol guide. Doses for these indications differ by an order of magnitude from the Simeons protocol.

Medical Disclaimer: This article is educational. The HCG diet is not approved by the FDA for weight loss. Severe very-low-calorie diets are associated with serious adverse events including gallstones, electrolyte imbalances, and cardiac arrhythmias, and should not be undertaken without medical supervision. Anyone considering HCG for any indication should review their personal history with a qualified clinician. Information here reflects published clinical evidence as of 2026.

Written by

Sophie Chen

Pharmaceutical Content Researcher · 8 years experience

Sophie Chen is a pharmaceutical content researcher with 8 years covering generic medication access and clinical pharmacology. She specialises in international regulatory frameworks, bioequivalence standards, and patient-facing education on therapeutic drug classes. She is not a clinician.