Abstract
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Background:
Obesity is a major threat to public health given its strong links with
cardiometabolic morbidity and premature mortality. One-third of obese adults
are metabolically healthy, but little is known about modifiable determinants
of this state or its progression over time. Aims: To determine whether
physical activity and sedentary behaviour distinguish healthy from unhealthy
obesity, and whether healthy obese adults have increased risk for developing
metabolic ill-health and type 2 diabetes. Methods: Data were drawn from up to
5427 men and women participating in the Whitehall II cohort study.
Normal-weight, overweight, and obese adults were considered healthy if they
had <2 of 5 metabolic risk factors (hypertension, low HDL-cholesterol,
high triglycerides, high blood glucose, and insulin resistance). Associations
of self-reported moderate-to-vigorous physical activity and leisure sitting
time with prevalence and 15-year incidence of metabolic risk factor
clustering were examined among healthy obese adults. Differences in
accelerometer-assessed total physical activity were also examined between
healthy and unhealthy obese groups. Metabolic risk factor incidence among
initially healthy obese adults was described, and published risk estimates of
incident type 2 diabetes were systematically searched and meta-analysed.
Results: Neither high self-reported moderate-to-vigorous physical activity
nor low self-reported leisure sitting was associated with health among obese
adults. Higher total physical activity among healthy versus unhealthy obese
adults was evident through accelerometer assessment only (p=0.002). After 20
years, 52% of initially healthy obese adults were unhealthy obese, with
insulin resistance being most commonly incident. Meta-analyses of 8 studies
indicated that healthy obese adults have 4.03 (95% CI=2.66-6.09) times
greater risk of incident type 2 diabetes than healthy normal-weight adults.
Conclusions: Higher physical activity rather than lower sedentary behaviour
distinguishes healthy from unhealthy obesity. Healthy obesity is strongly
linked with future insulin resistance and type 2 diabetes, suggesting that it
is not a harmless condition.
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