Body fat and risk of all-cause mortality: a systematic review and dose-response meta-analysis of prospective cohort studies.
Level 3 - non-randomized controlled study
Systematic review and dose-response meta-analysis of prospective cohort studies
PubMed 35717418 · doi:10.1038/s41366-022-01165-5
What was done
Systematic review and dose-response meta-analysis searching PubMed, Scopus, and Web of Science up to June 2021. The authors evaluated prospective cohort studies examining associations between body fat percentage (BF%), fat mass (FM), fat mass index (FMI), visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT) and all-cause mortality in the general population. Relative risks were pooled using random-effects models across 35 cohorts comprising 923,295 participants and 68,389 deaths.
What was found
All-cause mortality hazard ratios were 1.11 (95% CI: 1.02 to 1.20; I2 = 93%, n = 11) per 10% increase in BF% in general adults, and 0.92 (95% CI: 0.79 to 1.06; I2 = 76%, n = 7) in adults over 60 years. Hazard ratios were 1.06 (95% CI: 1.01 to 1.12; I2 = 86%, n = 10) per 5 kg increase in FM; 1.11 (95% CI: 1.06 to 1.16; I2 = 79%, n = 7) per 2 kg/m2 increase in FMI; 1.17 (95% CI: 1.03 to 1.33; I2 = 72%, n = 8) per 1-SD increase in VAT; and 0.81 (95% CI: 0.66 to 0.99; I2 = 59%, n = 6) per 1-SD increase in SAT. A J-shaped relationship was observed for BF% and FM, with the lowest mortality risk observed at 25% BF% and 20 kg FM.
Why it matters
This review distinguishes the risk profiles of total, visceral, and subcutaneous fat depots, showing that general adiposity and visceral fat track with higher mortality in a non-linear pattern, whereas subcutaneous fat shows an inverse relationship.
Limits
All included data are observational and prone to residual confounding and reverse causation from baseline occult disease. Heterogeneity across studies was high across most endpoints (I2 values 59% to 93%). Body fat measurement methods, covariate adjustments, and follow-up durations varied substantially across cohorts.