Increased body fat is independently and negatively related with cardiorespiratory fitness levels in children and adolescents with normal weight.
BACKGROUND
Body mass index (BMI) is related with cardiorespiratory fitness (CRF), but less is known regarding the combined relationships between BMI and body fat (BF) on CRF.


METHODS
Cross-sectional study included 2361 girls and 2328 boys aged 10–18 years living in the area of Lisbon, Portugal. BMI was calculated by measuring height and weight, and obesity was assessed by international criteria. BF was assessed by bioimpedance. CRF was assessed by the 20-m shuttle run and the participants were classified as normal-to-high or low-CRF level according to Fitness gram criterion-referenced standards.


RESULTS
The prevalence of low CRF was 47 and 39% in girls and boys, respectively. The corresponding values for the prevalence of obesity were 4.8 and 5.6% (not significant) and of excess BF of 12.1 and 25.1% (P <0.001), respectively. In both sexes, BMI and BF were inversely related with CRF: r = – 0.53 and – 0.45 for BMI and % BF, respectively, in boys and the corresponding values in girls were – 0.50 and – 0.33 (all P <0.01). When compared with a participant with normal BMI and BF, the odds ratios (95% confidence interval) for low CRF were 1.94 (1.46–2.58) for a participant with normal BMI and high BF, and 6.19 (5.02–7.63) for a participant with high BMI and high BF.


CONCLUSIONS
The prevalence of low-CRF levels is high in Portuguese youths. BF negatively influences CRF levels among children/adolescents with normal BMI.
Clinical Trials Unit, University Hospital (CHUV), Institute of Social and Preventive Medicine, University of Lausanne, 17 rue du Bugnon, Lausanne, Switzerland. Pedro-Manuel.Marques-Vidal@chuv.ch
Pedro
P
Marques-Vidal
Gisela
G
Marcelino
Paula
P
Ravasco
João Miguel
JM
Oliveira
Fred
F
Paccaud
D050154:Adiposity; D000293:Adolescent; D015992:Body Mass Index; D001835:Body Weight; D016009:Chi-Square Distribution; D002648:Child; D003430:Cross-Sectional Studies; D017097:Electric Impedance; D005080:Exercise Test; D005260:Female; D006801:Humans; D008297:Male; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D016017:Odds Ratio; D010809:Physical Fitness; D011174:Portugal / Q000453:epidemiology; D015995:Prevalence; D012016:Reference Values; D018570:Risk Assessment; D012307:Risk Factors