Chris Kresser on saturated fat: what the evidence says · JRE #1175

What the evidence says 01 / RECORD

Kresser claimed that no meta-analysis of randomized controlled trials or prospective cohort studies has found any significant difference in all-cause mortality from dietary fat interventions. For saturated fat specifically, this is broadly consistent with current RCT evidence: a 2020 Cochrane review of 15 trials (56,675 participants) found no significant effect on all-cause mortality (RR 0.96, 95% CI 0.90-1.03) or cardiovascular mortality (RR 0.95, 95% CI 0.80-1.12), though the same review found a statistically significant 17% reduction in combined cardiovascular events (RR 0.83, 95% CI 0.70-0.98), a different endpoint than mortality; a 2025 meta-analysis of 9 RCTs (13,532 participants) likewise found no significant mortality difference (all-cause OR 1.01, 95% CI 0.89-1.14). However, a 2015 BMJ meta-analysis of prospective cohort studies (de Souza et al.) found that while saturated fat intake showed no association with all-cause mortality (RR 0.99, 95% CI 0.91-1.09), trans fat intake was associated with a statistically significant 34% increase in all-cause mortality (RR 1.34, 95% CI 1.16-1.56) pooled across cohort studies. As an unqualified claim spanning all dietary fat types and all meta-analyses, the statement is overstated, since at least one meta-analysis of cohort data has found a significant all-cause mortality association for a dietary fat (trans fat). Narrowed specifically to saturated fat and mortality, the claim is largely consistent with the current evidence base.