Christine Delisle Nyström
Children with obesity who have a high level of cardiorespiratory fitness have a lower cardiometabolic risk and less insulin resistance when compared with children with obesity who are not fit, according to findings published in Diabetes Care.
“The fat-but-fit paradox denotes individuals who are considered obese but have moderate to high [cardiorespiratory fitness], and evidence indicates that fat-but-fit adults do not have a significantly higher risk of mortality from cardiovascular disease than normal-weight, unfit adults,” Christine Delisle Nyström, a nutritionist and doctoral student in the department of biosciences and nutrition at the Karolinska Institute in Huddinge, Sweden, and colleagues wrote. “In children/adolescents, evidence regarding this paradox is inconsistent.”
Nystrom and colleagues analyzed pooled, cross-sectional data from three Spanish studies led by researchers from the University of Granada, University of Navarra and the University of Castilla-la-Mancha involving 1,247 children aged 8 to 11 years. Children provided fasting blood samples, and researchers calculated two cardiometabolic risk scores based on sex- and age-specific z scores for triglycerides, HDL cholesterol, glucose, the average of systolic and diastolic blood pressure, and homeostatic model assessment of insulin resistance (HOMA-IR). Children were classified into BMI categories using criteria from the World Obesity Federation. Cardiorespiratory fitness was assessed with a 20-m shuttle run test, and children were classified as fit (> 20th percentile) or unfit, using age- and sex-specific centiles.
In regression analysis, researchers observed a linear association between the risk score and BMI categories. Every incremental rise in BMI category was associated with a 0.5 standard deviation (SD) higher cardiometabolic risk score (beta = 0.474; P < .001). In analysis of covariance, children with overweight, mild obesity, severe obesity or morbid obesity had 0.4, 0.8, 1.4 and 1.6 SD higher cardiometabolic risk scores in their increasing respective BMI categories when compared with normal-weight children.
A trend was found showing that as BMI categories rose, cardiorespiratory fitness attenuated the risk score, with the biggest differences observed in the children with the greatest obesity (20.8 SD); however, this attenuation was significant only in mild obesity (20.2 SD; P = .048). Normal-weight, unfit children had a lower risk score than fit children with obesity (P < .001); however, a significant reduction in the risk score was found in fit children with obesity compared with unfit children (–0.4 SD; P = .027).
Researchers also observed a trend for that cardiorespiratory fitness attenuated both cardiometabolic risk scores, particularly in the highest BMI categories. For both risk scores, children who were fit and had mild obesity, severe or morbid obesity saw 0.1, 0.2 and 0.8 SD lower cardiometabolic risk scores, respectively, when compared with unfit counterparts; however, the difference was only significant in mild obesity. Similarly, cardiorespiratory fitness also attenuated insulin resistance, but was significant only among children with mild obesity. Researchers also found differences in cardiometabolic risk scores and HOMA-IR between fit and unfit children with obesity, as well as fit and unfit normal-weight children (P < .001 for all). Cardiometabolic risk scores were –0.4 SD and –0.5 SD lower in fit children with obesity vs. unfit children with obesity; HOMA-IR was –0.4 SD lower, according to researchers.
“Obesity treatment is largely focused on energy restriction, which is especially difficult to implement in children,” Nyström told Endocrine Today. “Promoting physical activity with the aim to increase cardiorespiratory fitness from an early age should be incorporated into childhood obesity treatment programs in order to aid obese children to have reduced cardiometabolic risk.”– by Regina Schaffer
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can be reached at the Karolinska Institute, Department of Biosciences and Nutrition, SE-171 77, Stockholm, Sweden; email: firstname.lastname@example.org.
Disclosures: The authors report no relevant financial disclosures.