What do we really know about physical activity in obese children and adolescents?

Physical activity is essential to the prevention and the treatment of childhood obesity. The main notions established so far leads to conclude that lifestyle programmes are more efficient than other ones in treating obese children. From a metabolic point of view, weight loss should be easy to achieve and weight regain easy to avoid: obese children have enhanced energy expenditure and increased fatty acid oxidation when compared to their lean counterparts. Since this is not the case, some underlying assumptions need to be re-examined. Psychomotor and social aspects are almost constantly left apart when childhood obesity is targeted. Furthermore, differences in mechanical energy output and biological maturation at different ages and between boys land girls are not usually taken into account. Some concepts such as the criteria on which anaerobic conditions are defined in obese children may also prove to be inadequate. Insulin resistance ought to be taken into account in that respect. The mechanical approach of energy expenditure helps demonstrating how a single bout of exercise, for example a vertical jump, can be extremely energy demanding. Psychomotor investigations are so far almost non existent while the first data show that its seems critical to integrate this clinical approach in the general evaluation of obese children. Obese children face a new paradox: they exhibit an adavanced growth pattern but a delayed development of some psychomotor skills. No data are available so far on how the expected metabolic changes during childhood adapts to this conflicting situation. Merging fields of competence seems now mandatory, and hopefully promising, to achieve better results in both the prevention and the treatment of childhood obesity through physical activity.