Introduction: Tirzepatide, a dual glucose-dependent insulinotropic polypeptide (GIP) and
glucagon-like peptide-1 (GLP-1) receptor agonist, produces substantial weight loss and
glycaemic improvement in people with and without type 2 diabetes mellitus (T2DM).
Obesity pharmacotherapy may influence household behaviours and indirectly affect
untreated cohabitants, but no prior report has described such an effect.
Patient main concerns and findings: A cohabiting couple presented with obesity. The female
partner (Patient A; no diabetes) sought weight loss therapy; the male partner (Patient B) had
long-standing T2DM managed with insulin. Both partners were motivated to lose weight but
had previously been unsuccessful through diet alone.
Primary diagnoses, interventions, and outcomes: Patient A began tirzepatide through a
pharmacy-supervised weight management programme (escalated to 5 mg weekly). Patient B
did not receive any pharmacotherapy but lived in the same household. Over 32 weeks,
Patient A lost > 30 % of baseline weight. Patient B lost 13 % of baseline weight, HbA1c fell
from 9.5 % to 6.1 %, and insulin requirements declined by approximately 70 %. These
outcomes paralleled those reported in tirzepatide clinical trials despite absence of
medication in Patient B.
Conclusion: This case illustrates potential household-level or “vicarious” efficacy of anti obesity pharmacotherapy. Environmental and behavioural changes in one partner may yield
indirect metabolic benefits for untreated cohabitants. Recognition of such effects could
inform patient counselling, cost-effectiveness assessments, and future research into family-based obesity care.