Healthy obesity and risk of accelerated functional decline and disability

Background/Objectives: Some obese adults have a normal metabolic profile and are considered ‘healthy’, but whether they experience faster ageing than healthy normal-weight adults is unknown. We compared decline in physical function, worsening of bodily pain, and likelihood of future mobility limitation and disability between these groups. Subjects/Methods: This was a population-based observational study using repeated measures over 2 decades (Whitehall II cohort data). Normal-weight (body mass index (BMI) 18.5-24.9kg/m²), overweight (25.0-29.9kg/m²), and obese (≥30.0kg/m29 ) adults were considered metabolically healthy if they had 0 or 1 of 5 risk factors (hypertension, low high density lipoprotein cholesterol, high triacylglycerol, high blood glucose, and insulin resistance) in 1991/94. Decline in physical function and worsening of bodily pain based on change in Short Form Health Survey items using 8 repeated measures over 18.8 years (1991/94-2012/13) was compared between metabolic-BMI groups using linear mixed models. Odds of mobility limitation based on objective walking speed (slowest tertile) and of disability based on limitations in ≥1 of 6 basic activities of daily living, each using 3 repeated measures over 8.3 years (2002/04-2012/13), were compared using logistic mixed models. Results: In multivariable-adjusted mixed models on up to 6635 adults (initial mean age 50 years; 70% male), healthy normal-weight adults experienced a decline in physical function of -3.68 (95% CI=-4.19, -3.16) score units per decade; healthy obese adults showed an additional -3.48 (-4.88, -2.08) units decline. Healthy normal-weight adults experienced a -0.49 (-0.12, 1.11) score unit worsening of bodily pain per decade; healthy obese adults had an additional -2.23 (-0.69, -3.78) units worsening. Healthy obesity versus healthy normal weight conferred 3.39 (2.29, 5.02) times higher odds of mobility limitation and 3.75 (1.94, 7.24) times higher odds of disability. Conclusions: Our results suggest that obesity, even if metabolically healthy, accelerates age-related declines in functional ability and poses a threat to independence in older age.