1. ^*Department of Medical Physiology, School of Medicine, Spain
2. ^‡Department of Physical Education and Sport, School of Sport Sciences, University of Granada, Spain;
3. ^†European Union Health Sciences, University of Zaragoza, Zaragoza, Spain;
4. ^§Immunonutrition Research Group, Department of Metabolism and Nutrition, Consejo Superior de Investigaciones Científicas, Madrid.

Correspondence: Francisco B. Ortega Department of Medical Physiology, School of Medicine, University of Granada, Granada 18071, Spain. E-mail: ortegaf@ugr.es

^*The costs of publication of this article were defrayed, in part, by the payment of page charges. This article must, therefore, be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Received 3 October 2005; Revised  0000; Accepted 6 December 2006.

Abstract

Objective: To determine whether physical activity, sedentary activities, and/or cardiorespiratory fitness are related to waist circumference in adolescents, as previously reported in adults.

Research Methods and Procedures: The study subjects were a representative sample of Spanish adolescents (N = 2859; 1357 boys, 1502 girls; age, 13 to 18.5 years), all of whom were involved in the AVENA (Food and Assessment of the Nutritional Status of Adolescents) study. BMI, waist circumference, pubertal maturation status, and cardiorespiratory fitness were measured in all. Leisure-time physical activity, sedentary activities, active commuting to school, and socioeconomic status were assessed by self-reported questionnaires.

Results: No relationship was found between leisure-time physical activity and BMI or waist circumference. In contrast, and in both boys and girls and after adjustment for confounding variables, cardiorespiratory fitness was found to be inversely associated with waist circumference and BMI, independent of sedentary activities or physical activity (p 0.001). The maximum oxygen consumption explained 13% of the variance in waist circumference in boys and 16% in girls. Sedentary activities were independently and directly related to waist circumference in both boys and girls (p 0.05) and to BMI in boys (p 0.05). Sedentary activities explained 10% of the variance in waist circumference in boys and 18% in girls. The BMI-adjusted waist circumference was inversely correlated with cardiorespiratory fitness in overweight-obese boys (p 0.05) and showed a trend toward significance in girls (p 0.1).

Discussion: Both moderate to high levels of cardiorespiratory fitness and sedentary activities, but not physical activity, are associated with lower abdominal adiposity, as measured by waist circumference.