Childhood obesity seems to be increasing at a disturbing rate. Exercise and diet are recommended to combat this epidemic. Light and moderate physical activity is associated with health benefits, whereas intense physical activity is associated with normal BMI and low cardiovascular risk. The aim of this study was to assess the metabolic response to a graded exercise test (GXT) in children with different body weight. Eight boys and nine girls underwent a GXT on a treadmill according to Blake protocol. These children were 7-9 years old. The participants were divided into three groups according to their body weight: normal-weight, overweight, and obese. After GXT, lactate and HDL levels increased significantly in all three groups (p < 0.05). In this experimental trial, we show that HDL level increased after a single session of intense exercise in children regardless of body weight.
 Oláiz-Fernández, G., Rivera-Dommarco, J., Shamah-Levy, T., Rojas, R., Villalpando-Hernández, S. and Hernándezávila, M. (2006) Encuesta Nacional de Salud y Nutrición 2006. Cuernavaca, México: Instituto Nacional de Salud Pública.
 Kraja, A.T., Province, M.A., Arnett, D., Wagenknecht, L., Tang, W., Hopkins, P.N., Djousse, L. and Borecki, I.B. (2007) Do inflammation and procoagulation biomarkers contribute to the metabolic syndrome cluster? Nutrition & Metabolism (Lond), 4, 28.
 Hill, J.O., Wyatt, H.R., Reed, G.W. and Peters, J.C. (2003) Obesity and the environment: Where do we go from here? Science, 299, 853-855.
 Gidding, S.S., et al. (2006) Higher self-reported physical activity is associated with lower systolic blood pressure: The dietary intervention study in childhood (DISC). Pediatrics, 118, 2388-2393.
 Kimm, S.Y., et al. (2005) Relation between the changes in physical activity and body-mass index during adolescence: A multicentre longitudinal study. Lancet, 366, 301-307. http://dx.doi.org/10.1016/S0140-6736(05)66837-7
 Ferguson, M.A., et al. (1999) Effects of exercise training and its cessation on components of the insulin resistance syndrome in obese children. International Journal of Obesity and Related Metabolic Disorders, 23, 889-895.
 Kokkinos, P., et al. (2008) Exercise capacity and mortality in black and white men. Circulation, 117, 614-622.
 Macias-Cervantes, M.H., Malacara, J.M., Garay-Sevilla, M.E. and Diaz-Cisneros, F.J. (2009) Effect of recreational physical activity on insulin levels in Mexican/Hispanic children. European Journal of Pediatrics, 168, 1195-1202. http://dx.doi.org/10.1007/s00431-008-0907-7
 Zorba, E., Cengiz, T. and Karacabey, K. (2011) Exercise training improves body composition, blood lipid profile and serum insulin levels in obese children. Journal of Sports Medicine and Physical Fitness, 51, 664-669.
 Hayashino, Y., Jackson, J.L., Fukumori, N., Nakamura, F. and Fukuhara, S. (2012) Effects of supervised exercise on lipid profiles and blood pressure control in people with type 2 diabetes mellitus: a meta-analysis of randomized controlled trials. Diabetes Research and Clinical Practice, 98, 349-360.
 Woo, J., Shin, K.O., Yoo, J.H., Park, S. and Kang, S. (2012) The effects of detraining on blood adipokines and antioxidant enzyme in Korean overweight children. European Journal of Pediatrics, 171, 235-243.
 Pangrazi, R.P., Beighle, A., Vehige, T. and Vack, C. (2003) Impact of promoting lifestyle activity for youth (PLAY) on children’s physical activity. Journal of School Health, 73, 317-321.
 Stephens, B.R., Granados, K., Zderic, T.W., Hamilton, M.T. and Braun, B. (2011) Effects of 1 day of inactivity on insulin action in healthy men and women: Interaction with energy intake. Metabolism, 60, 941-949.
 Macias-Cervantes, M.H., Diaz-Cisneros, F.J. and Hagang, D. (2007) Acute effect of maximal treadmill exercise upon fasting insuline levels in children with elevated levels of insuline. Medicine & Science in Sports & Exercise, 39, S456.
 Cole, T.J., Bellizzi, M.C., Flegal, K.M. and Dietz, W.H. (2000) Establishing a standard definition for child overweight and obesity worldwide: international survey. BMJ, 320, 1240-1243.
 Couillard, C., et al. (2001) Effects of endurance exercise training on plasma HDL cholesterol levels depend on levels of triglycerides: Evidence from men of the health, risk factors, exercise training and genetics (HERITAGE) Family Study. Arteriosclerosis, Thrombosis, and Vascular Biology, 21, 1226-1232.
 Elosua, R. (2005) Physical activity. An efficient and underused way of preventing cardiovascular disease from childhood to old age. Revista Espanola de Cardiología, 58, 887-890. http://dx.doi.org/10.1157/13078123
 Haney, E.M., Huffman, L.H., Bougatsos, C., Freeman, M., Steiner, R.D. and Nelson, H.D. (2007) Screening and treatment for lipid disorders in children and adolescents: Systematic evidence review for the US preventive services task force. Pediatrics, 120, e189-e214.
 Mustelin, L., et al. (2008) Acquired obesity and poor physical fitness impair expression of genes of mitochondrial oxidative phosphorylation in monozygotic twins discordant for obesity. American Journal of Physiology— Endocrinology and Metabolism, 295, E148-E154.
 Lagally, K.M., et al. (2002) Perceived exertion, electromyography, and blood lactate during acute bouts of resistance exercise. Medicine & Science in Sports & Exercise, 34, 552-559.
 Franklin, B.A., Whaley, M.H., Howley, E.T. and Balady, G.J. (2000) ACSM’s guidelines for exercise testing and prescription. American College of Sports Medicine, Philadelphia. Lippincott Williams & Wilkins.
 Williams, J.R., Armstrong, N. and Kirby, B.J. (1990) The 4 mM blood lactate level as an index of exercise performance in 11-13 year old children. Journal of Science and Medicine, 8, 139-147.
 Denadai, B.S., Greco, C.C. and Teixeira, M. (2000) Blood lactate response and critical speed in swimmers aged 10-12 years of different standards. Journal of Science and Medicine, 18, 779-784.
 Tolfrey, K. and Armstrong, N. (1995) Child-adult differences in whole blood lactate responses to incremental treadmill exercise. British Journal of Sports Medicine, 29, 196-199. http://dx.doi.org/10.1136/bjsm.29.3.196
 Beneke, R., Hutler, M., Jung, M. and Leithauser, R.M. (2005) Modeling the blood lactate kinetics at maximal short-term exercise conditions in children, adolescents, and adults. Journal of Applied Physiology (1985), 99, 499-504.