Correspondence: Dr Jose M. Saavedra, PhD, Universidad de Extremadura, Facultad de Ciencias del Deporte, AFIDES Research Group, Avda, Universidad s/n, Caceres 10003, Spain. Email: jsaavdra@unex.es (Received 1 September 2010 ; final version received 30 March 2011) REVIEW ARTICLE Improvement of aerobic fitness in obese children: a meta-analysis JOSE M. SAAVEDRA, YOLANDA ESCALANTE & ANTONIO GARCIA-HERMOSO Universidad de Extremadura, Facultad de Ciencias del Deporte, AFIDES Research Group , Spain Abstract The purpose of this meta-analysis was to assess the effectiveness of diverse interventions in aerobic fitness adjusted for weight in obese children. A computerized search of seven databases was carried out using keywords. Effect sizes and 95% confidence intervals were calculated, and the heterogeneity of the studies was assessed using Cochran’ s Q statistic applied to the effect size means. Nine studies were selected for review as satisfying the inclusion criteria ( n patients = 311). The conclusions of the meta-analysis were: (i) the programs based on aerobic exercise have a moderate positive effect on aero- bic fitness; (ii) the programs based on aerobic exercise lasting more than 12 weeks (3000 minutes total exercise time) in three sessions per week (more than 60 min per session) obtain better results; (iii) overall, combined programs fail to achieve improvements in aerobic fitness; and (iv) few randomized clinical trials have been conducted. Key words: Aerobic program, combined program, obesity , peak VO 2 Introduction Obesity is considered to be a 21st century pandemic (1), with a prevalence of 7% affecting some 259 million adults (2). In children, the prevalence of obesity is 3% (3), and has multiple co-morbidities: dyslipidæmia, atheroma, hypertension, impaired vascular function, type-2 diabetes, metabolic syn- drome, osteoporosis, insulin resistance, and cardio- vascular disease, as well as most cancers, joint problems, sleep apnœa, steatohepatitis, and gastro- enterological problems (4). Furthermore, obesity, glucose intolerance, and hypertension in childhood are strongly associated with increased rates of pre- mature death from endogenous causes in this popu- lation (5). The probability of obese adolescents going on to become obese adults is 83% (6). However the mechanisms responsible for the increasing preva- lence of childhood obesity are not entirely understood, although lifestyle changes characterized by increased calorie consumption and decreased energy expendi- ture play a key role (7). A sedentary lifestyle leads to poor health-related physical fitness (HRPF), and this together with elevated body fatness is considered to be a strong predictor of cardiovascular disease in youth (8). One component of HRPF is the maximum oxygen uptake (peak VO 2 ) (9). Peak VO 2 is the greatest amount of oxygen a person can take in from inspired air while performing dynamic exercise involving a large part of their total muscle mass (10). The decrease in peak VO 2 has been associated with increased car- diovascular and all-cause mortality rates (11). This component of aerobic fitness not only determines performance in a wide range of activities, but is also a parameter related to health (12). Thus, peak VO 2 serves as an indicator of the limits of cardiovascular function as well as of the individual’ s capacity for endurance exercise (13). In the young in general, improvement of aerobic fitness through physical training is well documented (12). In obese children, however, such improvement is less clear (14) since, for physical, social, and psy- chological reasons, they are poorly motivated towards exercise (15). Thus, reduced values of cardiopulmo- nary exercise performance have been reported in obese adolescents (16), and obese children usually spend less time in moderate and vigorous physical activities (17). They therefore have lower aerobic International Journal of Pediatric Obesity, 2011; 6: 169–177 ISSN Print 1747-7166 ISSN Online 1747-7174 © 2011 Informa Healthcare DOI: 10.3109/17477166.2011.579975