Biohacking Kompakt

Peptide & Experimental

Tirzepatide (Mounjaro / Zepbound)

GLP-1 / GIP dual agonist · Mounjaro, Zepbound, LY3298176

13 min read 18 sources, checked November 13, 2026

In the BK-Score: Well supported – human evidence 10 out of 10, safety data 8 out of 10. The data in humans are solid.

All weight-loss injections and pills compared: approval, mechanism and trial results

Tirzepatide activates two gut hormone receptors at once and achieves the highest weight-loss figures in its drug class. The large cardiovascular outcome trial, however, missed superiority over an older comparator drug, and after stopping, the weight comes back.

What tirzepatide is

Tirzepatide is a prescription drug that acts as a dual agonist at the GLP-1 and GIP receptors, that is, at two receptors for the body's own gut hormones at once. In the European Union it is approved under the brand name Mounjaro, for both indications; Zepbound is the brand name in the US.

What is rated is the state of knowledge, not the substance. The trial program is large and methodologically strong, but younger than the one for semaglutide. Accordingly, there are fewer long-term data.

How it works

Activating the GLP-1 receptor slows gastric emptying, increases satiety and improves insulin secretion. GIP acts synergistically on insulin secretion and satiety. Targeting both receptors explains why weight loss is greater than with pure GLP-1 receptor agonists.

A stronger effect on weight, however, does not automatically mean a stronger effect on disease events. Exactly this transfer is the open point in the data.

Molecular target

  • Agonist Gastric inhibitory polypeptide receptor Gene GIPR · UniProt P48546
  • Agonist Glucagon-like peptide 1 receptor Gene GLP1R · UniProt P43220

Data: ChEMBL, UniProt · assigned automatically, as of November 12, 2026. A known target does not mean an effect in humans is established.

What is well supported

  • The co-primary endpoints were met. SURMOUNT-1 randomized 2,539 people without diabetes over 72 weeks. Weight loss was 15.0 percent on 5 mg, 19.5 percent on 10 mg and 20.9 percent on 15 mg versus 3.1 percent on placebo, each p less than 0.001. Depending on dose, 50 and 57 percent of participants, respectively, lost at least 20 percent of their weight, versus 3 percent on placebo.
  • More weight loss than semaglutide in a head-to-head trial. SURMOUNT-5 compared both drugs in 751 adults with obesity but without type 2 diabetes over 72 weeks, each at the highest tolerated dose. Weight fell by 20.2 versus 13.7 percent. The trial was open-label, meaning not blinded, and funded by the manufacturer.
  • Noninferiority was shown against an active comparator arm. SURPASS-CVOT tested 13,165 people with type 2 diabetes and atherosclerotic cardiovascular disease over a median of 46.9 months, not against placebo but against dulaglutide. The primary endpoint occurred in 12.2 versus 13.1 percent, HR 0.92 (95.3 percent confidence interval 0.83 to 1.01); noninferiority was reached with p equal to 0.003. An active comparator arm is the tougher test. Based on it, the FDA approved Mounjaro on 2026-08-28 to reduce cardiovascular risk in type 2 diabetes.
  • Fewer breathing pauses in sleep apnea. In SURMOUNT-OSA, in people with obesity and moderate to severe obstructive sleep apnea, the apnea-hypopnea index fell from around 50 events per hour by 25.3 versus 5.3 events on placebo after 52 weeks, roughly by half.
  • Approved for two indications. The European Medicines Agency approved Mounjaro on 2022-09-15, for type 2 diabetes and for weight management. The European public assessment report is publicly available.
  • With continued treatment, the loss is maintained. In the randomized withdrawal SURMOUNT-4, 670 people, after a 36-week lead-in (20.9 percent loss), lost a further 5.5 percent by week 88 with continued treatment, while the placebo group regained 14.0 percent, difference 19.4 percentage points (21.2 to 17.7), p less than 0.001. At least 80 percent of the loss was maintained by 89.5 percent of those continuing treatment versus 16.6 percent.

What the studies show

SURMOUNT-1: the weight figures

Jastreboff 2022 (NEJM) randomized 2539 people without diabetes over 72 weeks. The co-primary endpoints were met: weight loss of 15.0 percent (5 mg), 19.5 percent (10 mg) and 20.9 percent (15 mg) versus 3.1 percent on placebo, each p<0.001. At least 5 percent loss was reached by 85, 89 and 91 percent, respectively, versus 35 percent; at least 20 percent loss by 50 and 57 percent versus 3 percent. The trial does not show that disease events or mortality decrease.

SURMOUNT-5: the head-to-head comparison with semaglutide

Aronne 2025 (NEJM) randomized 751 adults with obesity but without type 2 diabetes to tirzepatide or semaglutide, each at the highest tolerated dose, over 72 weeks. Weight loss was 20.2 percent (19.1 to 21.4) versus 13.7 percent (12.6 to 14.9), p<0.001, on average 22.8 versus 15.0 kg; waist circumference fell by 18.4 versus 13.0 cm. The trial ran at 32 sites in the US and Puerto Rico and was funded by Eli Lilly. It was open-label: both groups knew what they received, which makes it more prone to bias than a blinded trial. It did not measure hard endpoints.

SURPASS-CVOT: superiority missed

Nicholls 2025 (NEJM) compared tirzepatide, active-controlled, against dulaglutide in 13,165 people with type 2 diabetes and atherosclerotic cardiovascular disease over a median of 46.9 months. The primary endpoint of cardiovascular death, heart attack and stroke occurred in 12.2 versus 13.1 percent, hazard ratio 0.92 (95.3 percent confidence interval 0.83 to 1.01). Noninferiority was reached (p=0.003), superiority was missed (p=0.09). There was no placebo arm. Dulaglutide itself has been shown to reduce cardiovascular events. Based on SURPASS-CVOT, the US Food and Drug Administration approved Mounjaro on 2026-08-28 to reduce the risk of major cardiovascular events in adults with type 2 diabetes at high risk. In June 2026 the EMA acknowledged the risk reduction but did not grant a separate indication, because this use is already covered by the existing authorization; the data are in the product information.

SUMMIT: heart failure with obesity

Packer 2025 (NEJM) tested 731 people with heart failure with preserved ejection fraction and a BMI of at least 30, double-blind against placebo, over a median of 104 weeks. Cardiovascular death or worsening heart failure occurred in 9.9 versus 15.3 percent, HR 0.62 (0.41 to 0.95). This was driven by fewer worsening events (8.0 versus 14.2 percent); there were 8 versus 5 cardiovascular deaths, HR 1.58 (0.52 to 4.83), too few events for a reliable conclusion. In January 2026 the EMA did not grant a separate indication: it is unclear whether the effect goes beyond the weight loss, and the use is covered by the weight management authorization.

SURMOUNT-OSA: sleep apnea

Malhotra 2024 (NEJM) studied adults with obesity and moderate to severe obstructive sleep apnea in two double-blind trials over 52 weeks, one without and one with positive airway pressure therapy. At baseline there were 51.5 and 49.5 apneas and hypopneas per hour (apnea-hypopnea index). The index fell by 25.3 versus 5.3 and by 29.3 versus 5.5 events per hour on placebo, each p<0.001. The FDA approved Zepbound for this in December 2024, in its words the first drug treatment option for certain patients; the EMA considered the use covered by the existing weight management authorization.

SURMOUNT-4: randomized withdrawal

Aronne 2024 (JAMA) moved 670 people into a randomized withdrawal after a 36-week lead-in phase with 20.9 percent weight loss. Between weeks 36 and 88, those continuing treatment lost a further 5.5 percent, while the placebo group regained 14.0 percent; difference 19.4 percentage points (17.7 to 21.2), p<0.001. At least 80 percent of the loss was maintained by 89.5 versus 16.6 percent.

This matches a meta-analysis in the BMJ (West 2026, 37 studies, 9,341 participants) on weight-loss medications overall: after stopping, weight returned by an average of 0.4 kg per month, faster than after behavioral programs, and cardiometabolic markers were projected to be back at baseline after about 1.4 years.

Composition of the weight loss

Rakhsha 2026 (Diabetes Obes Metab) examined in a network meta-analysis of 41 randomized trials with 2906 people what exactly is lost. On tirzepatide, fat mass fell by 10.70 kg (7.99 to 13.42), lean mass by 4.40 kg (1.22 to 7.58). Another analysis puts the lean mass share of weight loss at 25.4 percent (22.8 to 28.0).

Where the data stop

  • Better cardiovascular protection than with GLP-1 receptor agonists. SURPASS-CVOT achieved only noninferiority versus dulaglutide. Superiority was missed with p=0.09, and there was no placebo arm.
  • Fewer events or lower mortality through the weight loss. SURMOUNT-1 measured weight endpoints only. Transferring the percentages to disease outcomes is not supported by this trial.
  • A weight effect that persists after stopping. In the randomized withdrawal, the placebo group regained 14.0 percent between week 36 and week 88, while those continuing treatment kept losing. A meta-analysis on weight-loss medications overall puts the regain at an average of 0.4 kg per month.
  • A heart failure benefit independent of weight. In SUMMIT, mainly worsening heart failure events decreased; there were 8 versus 5 cardiovascular deaths. The EMA considers it open whether the effect goes beyond the weight loss.
  • A blinded head-to-head comparison with semaglutide. SURMOUNT-5 was open-label and funded by the manufacturer, and it did not measure hard endpoints.
  • Pure fat loss. Alongside 10.70 kg of fat mass, 4.40 kg of lean mass was lost, corresponding to 25.4 percent of the weight loss. Preservation of lean mass is not documented.

Status, approval and legal

In the EU the product is called Mounjaro, for both indications: the European Medicines Agency approved it on 2022-09-15 for type 2 diabetes and for weight management. The European public assessment report is publicly available, and the drug is prescription-only. Zepbound is the brand name in the US, where tirzepatide for weight loss has a separate approval.

New trials have not led to new indications in the EU so far. Three times the EMA reviewed the data and classified the use as covered by the existing authorization: for sleep apnea (December 2024), for heart failure with preserved ejection fraction (January 2026) and for reducing serious cardiovascular events (June 2026). The results on sleep apnea and cardiovascular events are in the product information. In the US, the FDA approved Zepbound in December 2024 for moderate to severe obstructive sleep apnea with obesity, and Mounjaro on 2026-08-28 to reduce cardiovascular risk in adults with type 2 diabetes.

Relevant for the situation in Germany: statutory health insurance does not cover weight reduction. Section 34(1) of the Social Code Book V excludes drugs for regulating body weight, and the Lower Saxony-Bremen State Social Court confirmed this for Mounjaro in May 2026. As of 2026-11-13 the law has not been changed. Tirzepatide is reimbursed for type 2 diabetes. In the promotion of the drug, the coverage point regularly goes unmentioned.

In the US, pharmacies were allowed to compound tirzepatide while it was on the FDA drug shortage list, from December 2022. The FDA declared the shortage resolved in October 2024 and confirmed this by declaratory order on 2024-12-19. The transition periods for compounding ended on 2025-02-18 for pharmacies and on 2025-03-19 for outsourcing facilities.

Safety

In SURPASS-CVOT, tirzepatide caused more gastrointestinal side effects than the comparator drug dulaglutide. The trial was active-controlled, so no comparison against placebo can be derived from it. In the head-to-head trial SURMOUNT-5, 2.7 percent on tirzepatide and 5.6 percent on semaglutide stopped treatment because of gastrointestinal side effects.

The second relevant point concerns body composition. A loss of 4.40 kg of lean mass alongside 10.70 kg of fat mass means that about a quarter of the weight lost does not come from fat tissue. Long-term data on the consequences of this share are not available.

BK-Score Well supported

Human evidence10
Mechanism9
Safety data8
Hype gap7
Track record of use8

Approved on the basis of the SURMOUNT and SURPASS programs; the dual receptor action is documented in humans. Fewer long-term data than for semaglutide, because it is younger. Coverage by statutory health insurance is excluded – that gets left out in the advertising.

The score rates the state of knowledge, not the substance. A high safety-data value means well studied – not harmless. A high track-record value means used long and widely – that is not proof of efficacy.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)

Frequently asked questions about tirzepatide (Mounjaro / Zepbound)

How much weight do people lose on tirzepatide?

In SURMOUNT-1, 2539 people without diabetes lost 15.0, 19.5 or 20.9 percent of their body weight over 72 weeks, depending on dose, versus 3.1 percent on placebo. In the higher dose groups, 50 and 57 percent of participants, respectively, lost at least 20 percent, versus 3 percent.

Does tirzepatide protect against heart attack and stroke?

Superiority has not been shown. In SURPASS-CVOT, with 13,165 people with type 2 diabetes and cardiovascular disease over a median of 46.9 months, tirzepatide was noninferior to the comparator dulaglutide, whose cardiovascular benefit is established; superiority was missed with p equal to 0.09. The event rate was 12.2 versus 13.1 percent, and there was no placebo arm. On this basis, the FDA approved Mounjaro on 2026-08-28 to reduce the risk of major cardiovascular events in adults with type 2 diabetes. The EMA considers this use covered by the existing authorization.

Is tirzepatide stronger than semaglutide?

For weight, yes, and a head-to-head trial now shows it too. In SURMOUNT-5 (NEJM 2025), 751 adults with obesity but without type 2 diabetes lost 20.2 percent of their body weight over 72 weeks on tirzepatide and 13.7 percent on semaglutide, each at the highest tolerated dose. The trial was open-label, meaning not blinded, and funded by the maker of tirzepatide. For hard cardiovascular endpoints there is no head-to-head comparison: semaglutide reduced them versus placebo in SELECT, while tirzepatide was noninferior to the GLP-1 drug dulaglutide in SURPASS-CVOT.

What happens after stopping tirzepatide?

The weight goes back up. In the randomized withdrawal of SURMOUNT-4, 670 people who had lost 20.9 percent in the lead-in phase regained 14.0 percent on placebo between weeks 36 and 88, while those who continued treatment lost a further 5.5 percent. The difference was 19.4 percentage points. A meta-analysis in the BMJ in 2026 of 37 studies with 9,341 participants found an average regain of 0.4 kg per month after stopping weight-loss medications, faster than after behavioral programs.

Do you lose muscle mass on tirzepatide?

Yes, to a measurable extent. A network meta-analysis of 41 randomized trials with 2906 people found, alongside a fat mass loss of 10.70 kg, a loss of 4.40 kg of lean mass. Another analysis puts the lean mass share of total weight loss at 25.4 percent, roughly a quarter of the weight lost.

Is tirzepatide approved in Germany?

Yes. In the EU the product is called Mounjaro for both uses: the European Medicines Agency approved it on 2022-09-15 for type 2 diabetes and for weight management, and it is prescription-only. Zepbound is the name in the US. German statutory health insurance does not pay for weight reduction, because Section 34(1) of the Social Code Book V excludes such drugs; the Lower Saxony-Bremen State Social Court confirmed this for Mounjaro in May 2026. As of 2026-11-13 the law has not been changed, so treatment for weight loss is paid out of pocket. Tirzepatide is reimbursed for type 2 diabetes.

The podcast episode (in German)

Episode 14

Tirzepatide (Mounjaro & Zepbound): The Strongest Approved Fat Burner, Fact-Checked

The podcast by Paul Höser (Episode 14) · with Paul & Paula. A fresh, positive AI dialogue episode about tirzepatide – the dual agonist (GLP-1 + GIP) behind Mounjaro and Zepbound. Why two hormone switches work better than one, what the SURMOUNT-1 trial (NEJM 2022, up to 20.9% weight across all participants) and the head-to-head duel SURPASS-2 against semaglutide showed, the GIP paradox, the US approval for sleep apnea – and the clear advantage: legal and under medical supervision instead of the gray market. Information only, no dosage or usage recommendation – prescription-only.

Listen on Spotify

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Information only, not medical advice and not a usage or dosage recommendation. Prescription-only and unapproved substances belong in a doctor's hands. Last updated: 2026-11-13.