Abstract
ObjectiveWe aimed to re-examine mortality risk estimates for metabolically healthy obesity by using a ‘stable’ healthy non-obese referent group.DesignProspective cohort study.MethodsParticipants were 5427 men and women (aged 65.9 ± 9.4 years, 45.9% men) from the English Longitudinal Study of Ageing. Obesity was defined as body mass index ≥30 kg/m2 (vs non-obese as below this threshold). Based on blood pressure, HDL cholesterol, triglycerides, glycated hemoglobin and C-reactive protein, participants were classified as ‘healthy’ (0 or 1 metabolic abnormality) or ‘unhealthy’ (≥2 metabolic abnormalities).ResultsTotally, 671 deaths were observed over an average follow-up of 8 years. When defining the referent group based on 1 clinical assessment, the unhealthy non-obese (hazard ratio (HR) = 1.22; 95% CI: 1.01, 1.45) and unhealthy obese (HR = 1.29; CI: 1.05, 1.60) were at greater risk of all-cause mortality compared to the healthy non-obese, yet no excess risk was seen in the healthy obese (HR = 1.14; CI: 0.83, 1.52). When we re-defined the referent group based on 2 clinical assessments, effect estimates were accentuated and healthy obesity was at increased risk of mortality (HR = 2.67; CI: 1.64, 4.34).ConclusionAn unstable healthy referent group may make ‘healthy obesity’ appear less harmful by obscuring the benefits of remaining never obese without metabolic dysfunction.
Highlights
Termed ‘metabolically healthy obesity’, population-based studies have identified an obesity phenotype that is not accompanied by a clustering of adiposity-associated cardio-metabolic risk factors [1]
Tendencies for metabolic decline and for developing type 2 diabetes are becoming clear [1], associations of healthy obesity with outcomes related to cardiovascular disease and mortality are less consistent [2, 3]. One explanation for these inconsistencies may be differences in the duration of follow-up used across studies, with those using shorter follow-up times tending to find no association between healthy obesity and outcomes [4, 5]
Studies that examine the risks of healthy obesity tend to rely on one-off measures of body mass index (BMI) and biomarkers of metabolic health
Summary
Termed ‘metabolically healthy obesity’, population-based studies have identified an obesity phenotype that is not accompanied by a clustering of adiposity-associated cardio-metabolic risk factors [1]. Tendencies for metabolic decline and for developing type 2 diabetes are becoming clear [1], associations of healthy obesity with outcomes related to cardiovascular disease and mortality are less consistent [2, 3]. One explanation for these inconsistencies may be differences in the duration of follow-up used across studies, with those using shorter follow-up times tending to find no association between healthy obesity and outcomes [4, 5].
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