Healthy obesity and objective physical activity

Abstract

Background: Disease risk is lower in metabolically healthy obese adults than in their unhealthy obese counterparts. Studies considering physical activity as a modifiable determinant of healthy obesity have relied on self-reported measures, which are prone to inaccuracies and do not capture all movements that contribute to health.

Objective: We aimed to examine differences in total and moderate-to-vigorous physical activity between healthy and unhealthy obese groups by using both self-report and wrist-worn accelerometer assessments.

Design: Cross-sectional analyses were based on 3457 adults aged 60-82 y (77% male) participating in the British Whitehall II cohort study in 2012-2013. Normal-weight, overweight, and obese adults were considered "healthy" if they had <2 of the following risk factors: low HDL cholesterol, hypertension, high blood glucose, high triacylglycerol, and insulin resistance. Differences across groups in total physical activity, based on questionnaire and wrist-worn triaxial accelerometer assessments (GENEActiv), were examined by using linear regression. The likelihood of meeting 2010 World Health Organization recommendations for moderate-to-vigorous activity (≥2.5 h/wk) was compared by using prevalence ratios.

Results: Of 3457 adults, 616 were obese [body mass index (in kg/m²) ≥30]; 161 (26%) of those were healthy obese. Obese adults were less physically active than were normal-weight adults, regardless of metabolic health status or method of physical activity assessment. Healthy obese adults had higher total physical activity than did unhealthy obese adults only when assessed by accelerometer (P = 0.002). Healthy obese adults were less likely to meet recommendations for moderate-to-vigorous physical activity than were healthy normal-weight adults based on accelerometer assessment (prevalence ratio: 0.59; 95% CI: 0.43, 0.79) but were not more likely to meet these recommendations than were unhealthy obese adults (prevalence ratio: 1.26; 95% CI: 0.89, 1.80).

Conclusions: Higher total physical activity in healthy than in unhealthy obese adults is evident only when measured objectively, which suggests that physical activity has a greater role in promoting health among obese populations than previously thought.

Keywords: epidemiology; metabolic health; metabolic risk factor clustering; obesity; physical activity.

FIGURE 1

Differences in total physical activity across metabolic and obesity phenotypes based on questionnaire and accelerometer assessments in the Whitehall II cohort study (n = 3457). Data are standardized z scores to allow comparability between measures. Models were adjusted for age, sex, ethnicity, occupational position, diet quality, smoking status, alcohol consumption, sleep duration, and presence of an illness that limits moderate or vigorous activity. Model fit was better with the accelerometer-based than with the questionnaire-based assessments (Akaike Information Criterion for fully adjusted models = 9149.87 and 9707.06, respectively).

FIGURE 2

Association of questionnaire- and accelerometer-assessed total physical activity and individual metabolic risk factors in the Whitehall II cohort study (n = 3457). Data are standardized z scores to allow comparability between measures. Case numbers (n) are as follows: hypertension = 2161; low HDL = 1593; high triacylglycerol = 572; high blood glucose = 1071; insulin resistance = 344; obesity = 616. Prevalence ratios are based on Poisson regression models with robust error variances. Models were adjusted for age, sex, and ethnicity. Reference groups reflect the absence of each individual metabolic risk factor under consideration.