Biohacking Kompakt

Peptide & Experimental

Tirzepatide (Mounjaro / Zepbound)

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

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.

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.

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.
  • 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.
  • 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.

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.

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.

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.
  • 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

Mounjaro was approved by the European Medicines Agency 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.

Relevant for the situation in Germany: coverage by statutory health insurance is excluded for the weight reduction indication. In the promotion of the drug, this point regularly goes unmentioned.

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.

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. “Safety data 9” means well studied – not harmless. “Track record of use 9” 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 over a median of 46.9 months, tirzepatide achieved only noninferiority versus dulaglutide; superiority was missed with p equal to 0.09. The event rate was 12.2 versus 13.1 percent. There was no placebo arm.

Is tirzepatide stronger than semaglutide?

For weight, the figures from the respective approval trials are higher, up to 20.9 percent versus 14.9 percent in STEP 1. These trials, however, were run separately and are not directly comparable. For hard cardiovascular endpoints, there is no proof of superiority for tirzepatide, whereas semaglutide has a positive outcome trial.

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.

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. Mounjaro received approval from the European Medicines Agency on 2022-09-15, for both type 2 diabetes and weight management, and is prescription-only. Coverage by German statutory health insurance is, however, excluded for the weight reduction indication, so treatment is paid out of pocket.

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, ~22% weight) and the head-to-head duel SURPASS-2 against semaglutide showed, the GIP paradox, approval even 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: 2026-09-13.