Body weight modifies the efficacy of lifespan-extending interventions in ad libitum-fed mice

In ITP ad libitum-fed male mice, each added standard deviation of attained adult weight made lifespan-extending treatments 6% more favourable (HR 0.94), especially when interventions lowered body weight (HR 0.90).

• Why it matters: Lifespan gains in ad libitum-fed mice may partly reflect rescue from adverse phenotypes in heavier, shorter-lived controls, so treatment efficacy may depend on body weight.
• What they did: The study analyzed body weight and survival for 33,780 mice across ITP experiments, testing whether treatment effects varied with attained adult weight and whether effects differed by sex and compound.
• The result: Median lifespan increase rose from 6.2% in the lightest pre-dosing weight quartile to 20.2% in the heaviest quartile, with control survival declining more steeply with weight than intervention survival.

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