Aerobic physical fitness in relation to blood lipids and fasting glycaemia in adolescents: Influence of weight status
Introduction
Cardiovascular disease (CVD) is the leading cause of death in developed countries. Although the clinical manifestations of CVD occur in middle adulthood, pathological data have shown that atherosclerosis begins in childhood and adolescence [1], [2], [3]. Disturbed plasma lipid profile is an important cardiovascular risk factor, capable of inducing atherosclerotic development [4], [5]. This has been early shown in adults, but holds also for children and adolescents. In fact, it has been recently demonstrated that plasma low density lipoprotein (LDL) cholesterol levels measured in childhood are a consistent predictor of carotid artery intima-media thickness in young adults who are still too young to experience coronary events [6], [7]. These, and other findings [8], [9], suggest that a primary goal in CVD prevention should be to keep a healthy plasma lipid profile since childhood [10], [11].
Fasting glycaemia also deserves some attention. In fact, fasting glucose has been proposed as a marker of loss of beta cell function and insulin response [12], and there are noticeable similarities in the cardiovascular risk factor profile in subjects with impaired fasting glycaemia and in subjects with impaired glucose tolerance [13].
Regular aerobic physical activity leads to a significant cardiovascular risk reduction, by improving the plasma lipid profile [14], [15]. Along the same line, increased aerobic physical fitness (which is in part the result of regular practice of aerobic physical activity) during adolescence has been associated not only with healthier blood lipids during these years [16], [17], but also later in life [18]. Therefore, it seems reasonable to initiate regular aerobic physical activity in childhood in order to prevent metabolic risk and CVD in adulthood.
The previous studies did not analyse possible associations with a metabolic composite index, but with single blood lipids. Therefore, our first aim was to explore associations between aerobic physical fitness not only with single blood lipids, but also with a composite index of blood lipids and fasting glycaemia in adolescents. Of note, only one study [19] analysed interactions between obesity measures and aerobic physical fitness in relation to a metabolic composite index, so we also tested a similar interaction in our population. Finally, to the best of our knowledge there are no studies providing minimal criterion standards of aerobic fitness in adolescents, associated with healthy metabolic outcomes. Therefore, we secondly aimed to set minimal criterion standards of aerobic fitness associated with a favourable lipid profile in adolescents.
Section snippets
Study population and design
This research was part of the AVENA study (Análisis y Valoración del Estado Nutricional en Adolescentes españoles [Assessment of Nutritional Status in Spanish Adolescents]), a population-based cross-sectional multicentric study of the aetiology and pathogenesis of obesity and related metabolic disorders during adolescence. The general methodology of the study, as well as the sample inclusion criteria, has been published elsewhere [20], [21]. Briefly, 2851 Spanish adolescents (1354 males and
Results
As expected, aerobic physical fitness was significantly higher in males compared with females for all ages (P < 0.001) (Fig. 1).
After general linear model analysis adjusted for age, sexual maturation and economic status, aerobic physical fitness was related to triglycerides (P = 0.004), HDL cholesterol (P = 0.013), and Apo A-I (P = 0.028) in male adolescents (Table 2). In females, aerobic fitness was only significantly related to HDL cholesterol (P = 0.045) (Table 2).
A composite index of blood lipids and
Discussion
Previous studies in children [16], [17], [35], [36] have shown associations between aerobic physical fitness and blood lipids. We also show here associations between aerobic fitness and single blood lipids, mainly in males. The only association found in girls in our study was to HDL cholesterol levels, but even the first quartile of aerobic physical fitness had mean HDL cholesterol levels of 57.2 ± 10.6 mg/dl, quite acceptable. This discrepancy is also noted by Boreham et al. [17], who revealed
Acknowledgements
This study was supported by the Spanish Ministry of Health, FIS (00/0015) and FEDER-FSE funds, CSD grants 05/UPB32/01 and 09/UPB31/03, the Spanish Ministry of Education (AP2002-2920, AP2003-2128, AP2004-2745), and grants from Panrico S.A., Madaus S.A. and Procter & Gamble S.A.
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