Body composition

How to read this chart

Was lean tissue preserved during weight loss?

Compare the treatment arms at the same visit. The chart shows average change from baseline in kilograms.
EMBRAZE uses 80% confidence intervals; BELIEVE shows ±1 standard error. These are not interchangeable, and overlapping arm intervals do not directly test the treatment contrast.
Lean-mass preservation does not establish better strength or function. Read the limitations and safety view alongside the measured effect.

Terms in this view

Confidence interval: A range expressing statistical uncertainty around an estimate. It is not the range of individual patients’ outcomes. A 95% interval procedure covers the true value in about 95% of repeated studies under its assumptions. Reference
Standard error: Uncertainty in an estimated average or effect because it comes from a sample. It differs from the spread between participants. Bars showing ±1 SE are not 95% confidence intervals. Reference
Lean mass versus strength: Lean mass is a body-composition measurement. Preserving it does not by itself show better strength, mobility or daily function; those outcomes need separate measurement. Reference

Figures include sources, study context and the current selection.

Efficacy and safety in two trials of muscle-preserving add-ons.

Compare study

Lean tissue

Change from baseline · Week 24

primary outcome

Tirzepatide + apitegromab−1.6 kg

Tirzepatide + placebo−3.5 kg

Change in kilograms · negative values mean loss

Whiskers: 80% confidence intervals. Adjusted means; measured by DXA body-composition scans.

1.9 kg less lean tissue lost with apitegromab. Difference between the plotted means. DXA lean tissue is not a direct measure of muscle strength.

Exact values & analysis details

Treatment	Change (kg)	80% confidence intervals
Tirzepatide + apitegromab	−1.6	−2.3 to −0.8
Tirzepatide + placebo	−3.5	−4.1 to −2.8

Adjusted least-squares means in treatment completers with evaluable DXA; baseline weight/lean mass, age and sex covariates. CIs are 80%, not 95%.

Safety also matters. Nausea, fatigue and headache were numerically more frequent with apitegromab. One participant in each group had a serious adverse event.

Both groups received tirzepatide.

Adding apitegromab reduced lean-tissue loss; fat loss was similar.

Larger, longer studies must establish effects on strength, durability and safety.

Study limitations. Small phase 2 completer analysis; no multiplicity adjustment. DXA lean mass is not muscle function; exploratory function showed no notable difference. Eight weeks after stopping both drugs, the lean-mass difference narrowed to 0.9 kg. No cross-trial ranking is implied.

Redrawn from reported results · Nature Medicine · Jun 8, 2026 Trial registry · NCT06445075

Explore the therapies: Apitegromab · Bimagrumab · Tirzepatide · Semaglutide