Shifts in waist-to-height ratio categories within tirzepatide groups: a post-hoc analysis of SURMOUNT-1
Sattar N, Tchang BG, Vincent RP, Wang H, Murphy M, Dunn JP
Journal of Endocrinological Investigation (2026) · n=2,538
Across 2,538 SURMOUNT-1 participants, 72 weeks of tirzepatide 10/15 mg moved 54.7% into a better waist-to-height-ratio category versus 9.6% with placebo, and 16.7% reached WHtR ≤0.49 — a non-obese-by-NICE-definition threshold — sustained to 176 weeks in the prediabetes subset.
This is a prespecified post-hoc analysis of the SURMOUNT-1 Phase 3 trial examining body-composition redistribution rather than weight loss alone. 2,538 adults with obesity (BMI ≥30) or overweight (BMI ≥27 with at least one obesity-related complication, excluding diabetes) were randomised to once-weekly tirzepatide 5, 10, or 15 mg or placebo plus lifestyle. The analysis groups participants by baseline waist-to-height ratio (WHtR) per the National Institute for Health and Care Excellence framework: ≤0.49, >0.49 to ≤0.59, and >0.59. At baseline 89.8% were in the highest-risk WHtR >0.59 category, 10.1% in the middle, and 0.1% at the safer ≤0.49 threshold.
After 72 weeks of tirzepatide 10/15 mg, 16.7% of participants achieved WHtR ≤0.49 and 54.7% improved their baseline WHtR category, versus 9.6% category-improvement with placebo. The prediabetes subset followed beyond week 72 retained the effect at 176 weeks: 12.2% achieved WHtR ≤0.49 and 46.4% improved category, compared with 9.3% with placebo. The mixed-model analysis confirmed sustained absolute WHtR reduction relative to placebo.
This is a post-hoc analysis of a trial primarily designed to measure percent body weight change; WHtR was not the primary endpoint. The baseline distribution is highly skewed — only three participants started at WHtR ≤0.49, so the "achievement" denominator is essentially the entire trial population starting elevated. The 176-week data are restricted to the prediabetes subset, not the full cohort.
WHtR is a derived anthropometric and depends on the precision of waist-circumference measurement at trial sites. The NICE WHtR framework is one of several visceral-adiposity heuristics — replacing BMI with WHtR does not introduce a true visceral-fat measurement (DXA / MRI), so the "cardiometabolic risk reduction" inference is by association with future-risk literature, not from imaging in this trial.
Co-authorship and funding include Eli Lilly employees responsible for the statistical work. Abstract-only extraction.
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