Level of physical activity and adiposity in children: relevance of sedentary behaviors

Department of Mother and Child, Biology-Genetics, Pediatrics Unit
University of Verona
Piazzale LA Scuro, 10
37134 Verona
Italy
E-mail: claudio.maffeis{at}univr.it

Dear Sir:

The main finding of the study by Ekelund et al (1) was that the amount of time devoted to physical activity explained <1% of the variation in fat mass in 10-y-old children. This conclusion apparently reduces the relevance of the intensity of physical activity in the maintenance of childhood obesity and seems to frustrate the reasonable expectancy for the role potentially played by exercise and physical activity both in the prevention and treatment of overweight.

The energy cost of weight-bearing activities is higher in obese than in nonobese children (2, 3). This finding promotes, by implication, the spontaneous reduction of time devoted to moderate-to-vigorous physical activity (MVPA) by the obese, as previously reported by others (3, 4). However, the higher cost of MVPA compensated the lower time spent in MVPA so that no difference in the cumulative energy expenditure for MVPA could be found between obese and nonobese children. However, obese children spend more energy and, interestingly, oxidize much more fat during light-intensity exercise than do nonobese children (5). Therefore, the time spent in sedentary or light-intensity physical activities as well as the ratio between sedentary and light-intensity physical activities could be more crucial than their absolute values or MVPA for both the development and the maintenance of obesity. Interestingly, the results of a recent study conducted in young children, which showed a clear relation between sedentary as well as light-intensity physical activity and overweight, seems to support this hypothesis (6). At present, a change from sedentary behavior to a more active lifestyle remains the cornerstone of strategies to prevent and treat childhood obesity.

ACKNOWLEDGMENTS

No conflicts of interest were declared by the author.

REFERENCES

1. Ekelund U, Sardinha LB, Anderssen SA, et al. Associations between objectively assessed physical activity and indicators of body fatness in 9- to 10-y-old European children: a population-based study from 4 distinct regions in Europe (the European Youth Heart Study). Am J Clin Nutr 2004;80:584–90.
2. Maffeis C, Schutz Y, Schena F, et al. Energy expenditure during walking and running in obese and nonobese prepubertal children. J Pediatr 1993;123(2):193–9.
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5. Maffeis C, Zaffanello M, Pellegrino M, et al. Nutrient oxidation during moderately intense exercise in obese prepubertal boys. J Clin Endocrinol Metab 2005;90(1):231–6.
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