Chronic inflammation appears to be a primary mechanism that links excess adipose tissue, fat in other words, with an increased risk of age-related medical conditions and early death. Become fat and you suffer far more inflammation than your thin peers, and that has a significant impact on your health over the years, even for comparatively modest gains in weight.
Here researchers demonstrate an association between increased mortality and a specific characteristic of fat tissue that doesn't appear to involve inflammation, however - so there must be other ways in which fat tissue sabotages your health and life expectancy:
Knowledge of adipose composition in relation to mortality may help delineate inconsistent relationships between obesity and mortality in old age. We evaluated relationships between abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) density, mortality, biomarkers, and characteristics. VAT and SAT density were determined from computed tomography scans in persons aged 65 and older, Health ABC (n = 2,735) and AGES-Reykjavik (n = 5,131), and 24 nonhuman primates (NHPs). Associations between adipose density and mortality (4-13 years follow-up) were assessed with Cox proportional hazards models. In NHPs, adipose density was related to serum markers and tissue characteristics.
Higher density adipose tissue was associated with mortality in both studies with adjustment for risk factors including adipose area, total fat, and body mass index. In women, hazard ratio [for] the densest quintile (Q5) versus least dense (Q1) for VAT density [was] 1.95 (Health ABC) and 1.88 (AGES-Reykjavik) and for SAT density, 1.76 (Health ABC) and 1.56 (AGES-Reykjavik). In men, VAT density was associated with mortality in Health ABC, 1.52, whereas SAT density was associated with mortality in both Health ABC, 1.58, and AGES-Reykjavik, 1.43. Higher density adipose tissue was associated with smaller adipocytes in NHPs. There were no consistent associations with inflammation in any group. Higher density adipose tissue was associated with lower serum leptin in Health ABC and NHPs, lower leptin mRNA expression in NHPs, and higher serum adiponectin in Health ABC and NHPs.
[We conclude that] VAT and SAT density provide a unique marker of mortality risk that does not appear to be inflammation related.