Cardiorespiratory Fitness and Adiposity in Metabolically Healthy Overweight and Obese Youth

Abstract

WHAT'S KNOWN ON THIS SUBJECT: Obesity is associated with cardiometabolic risk factors and chronic conditions, such as type 2 diabetes. However, a proportion of overweight and obese youth remain free from cardiometabolic risk factors and are considered metabolically healthy. WHAT THIS STUDY ADDS:This study provides insight into the determinants of cardiometabolic risk factors and the concept in health promotion of "fitness versus fatness." Hepatic lipid accumulation and not fitness level appears to drive cardiometabolic risk factor clustering among overweight and obese youth. abstract OBJECTIVE: Controversy exists surrounding the contribution of fitness and adiposity as determinants of the Metabolically Healthy Overweight (MHO) phenotype in youth. This study investigated the independent contribution of cardiorespiratory fitness and adiposity to the MHO phenotype among overweight and obese youth. METHODS:This cross-sectional study included 108 overweight and obese youth classified as MHO (no cardiometabolic risk factors) or non-MHO ($1 cardiometabolic risk factor), based on age-and genderspecific cut-points for fasting glucose, triglycerides, high-density lipoprotein cholesterol, systolic and diastolic blood pressure, and hepatic steatosis.RESULTS: Twenty-five percent of overweight and obese youth were classified as MHO. This phenotype was associated with lower BMI z-score (BMI z-score: 1.8 6 0.3 vs 2.1 6 0.4, P = .02) and waist circumference (99.7 6 13.2 vs 106.1 6 13.7 cm, P = .04) compared with non-MHO youth. When matched for fitness level and stratified by BMI z-score (1.6 6 0.3 vs 2.4 6 0.2), the prevalence of MHO was fourfold higher in the low BMI z-score group (27% vs 7%; P = .03). Multiple logistic regression analyses revealed that the best predictor of MHO was the absence of hepatic steatosis even after adjusting for waist circumference (odds ratio 0.57, 95% confidence interval 0.40-0.80) or BMI z-score (odds ratio 0.59, 95% confidence interval 0.43-0.80). CONCLUSIONS:The MHO phenotype was present in 25% of overweight and obese youth and is strongly associated with lower levels of adiposity, and the absence of hepatic steatosis, but not with cardiorespiratory fitness. Pediatrics 2013;132:e85-e92 Obesity is associated with a clustering of cardiometabolic risk factors, including hypertension, insulin resistance, inflammation, and dyslipidemia. 1 However, cardiometabolic risk factor clustering is not an obligatory consequence of obesity. In fact, 18% to 44% of obese individuals are free from cardiometabolic risk factors. 2,3 The absence of cardiometabolic risk factor clustering in obese individuals is associated with lower measures of adiposity, including lower total fat mass, 4 abdominal obesity, 5,6 visceral fat mass, 3,7,8 and the absence of ectopic lipid accumulation. 9 Surprisingly, little attention has been paid to the modifiable factors as determinants of this "Metabolically Healthy Overweight" (MHO) phenotype. 10,11 This is particularly important, as the identification of modifiable behaviors associa...

Role of Fitness in the Metabolically Healthy but Obese Phenotype: A Review and Update

“…In accordance previous literature in youth 29,50,51 , we suggest to exclude waist circumference among the criteria to be considered for MHO.…”

“…In addition, a summary of the characteristics of these studies is shown in Table 2. Surprisingly, 75% of the studies focused exclusively on women 20-28 and only 25% focused on both women and men (no study was focused only in men) [29][30][31] .…”

Longitudinal associations of lifestyle factors and weight status with insulin resistance (HOMA-IR) in preadolescent children: the large prospective cohort study IDEFICS

“…A large cross-sectional study among Spanish adults [23] provided evidence that PA is one of the main factors responsible for a healthy phenotype among the obese. Only few studies published results for adolescents and these showed no association between PA and metabolically healthy obesity [22, 52]. Further research in children is needed, as there are no studies on metabolically healthy obesity in children.…”

“…Metabolically healthy obesity is apparently associated with lower levels of adiposity in youth [22, 23] and a high level of physical activity (PA) in adults [22, 23]. Increased PA and cardiorespiratory fitness are also believed to attenuate the risk of cardiovascular disease, type 2 diabetes, and MS, independent of weight status [24].…”

Obesity Prevention in Childhood and Cardiovascular Health Later in Life: We Need to Get the Ball Rolling

“…It is fair to say that we are just beginning to understand this phenomenon. Most authors refer to the number of cardiometabolic risk factors when applying or introducing a definition of MHO, and prevalence of MHO in obese youths is estimated to be between 4.2% and 25% [10,11]. The birth weight and obesity rebound during early infancy have been suggested as influencing factors.…”