Stability of metabolically healthy obesity over 8 years: the English Longitudinal Study of Ageing.
OBJECTIVE
Metabolically healthy obesity possibly reflects a transitional stage before the onset of metabolic dysfunction, but few studies have characterised this transition. We examined the behavioural and biological characteristics of healthy obese adults that progressed to an unhealthy state over 8 years follow-up.


METHODS
Participants were 2422 men and women (aged 63.3±7.7 years, 44.2% men) from the English Longitudinal Study of Ageing. Obesity was defined as BMI ≥30 kg/m(2). Based on blood pressure (BP), HDL-cholesterol, triglycerides, HbA1c and C-reactive protein (CRP) participants were classified as 'healthy' (0 or 1 metabolic abnormality) or 'unhealthy' (≥2 metabolic abnormalities).


RESULTS
Over 8 years follow-up, 44.5% of healthy obese subjects had transitioned into an unhealthy state, compared to only 16.6 and 26.2% of healthy normal-weight and overweight adults respectively. Compared with healthy obese adults who remained stable, those who progressed to an unhealthy state were more likely to have high BP (75.0% vs 37.0%, age- and sex-adjusted odds ratio (OR) 8.9, 95% CI 4.7-17.0), high CRP (53.7% vs 17.0%, OR=8.6, 95% CI 4.1-18.0), high HbA1c (46.3% vs 5.9%, OR=13.8, 95% CI 6.1-31.2) and high triglycerides (45.4% vs 11.9%, OR=5.9, 95% CI 2.9-12.0) at follow-up, with excess risk remaining independent of lifestyle factors including self-reported physical activity. Progression to an unhealthy state was also linked with significant gains in waist circumference (B=2.7, 95% CI, 0.5-4.9 cm).


CONCLUSIONS
These data show that a healthy obesity phenotype is relatively unstable. Transition to an unhealthy state is characterised by multiple biological changes that are not fully explained by lifestyle risk factors.
National Centre for Sport and Exercise MedicineSchool of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UKDepartment of Epidemiology and Public HealthUniversity College London, London, UK National Centre for Sport and Exercise MedicineSchool of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UKDepartment of Epidemiology and Public HealthUniversity College London, London, UK m.hamer@lboro.ac.uk.
Mark
M
Hamer
National Centre for Sport and Exercise MedicineSchool of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UKDepartment of Epidemiology and Public HealthUniversity College London, London, UK.
Joshua A
JA
Bell
National Centre for Sport and Exercise MedicineSchool of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UKDepartment of Epidemiology and Public HealthUniversity College London, London, UK.
Severine
S
Sabia
National Centre for Sport and Exercise MedicineSchool of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UKDepartment of Epidemiology and Public HealthUniversity College London, London, UK.
G David
GD
Batty
National Centre for Sport and Exercise MedicineSchool of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UKDepartment of Epidemiology and Public HealthUniversity College London, London, UK.
Mika
M
Kivimäki
D000368:Aged; D000375:Aging / Q000378:metabolism*; D018450:Disease Progression; D004739:England; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D050177:Overweight / Q000378:metabolism*