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Pretilost je povezana s inzulinskom rezistencijom i rizikom za razvoj disglikemije. Izrazito pretili adolescenti te oni s visokim udjelom visceralne masti češće razvijaju metaboličke poremećaje. Povezanost kardiorespiratorne sposobnosti s metaboličkim rizikom u osoba s različitim stupnjevima pretilosti nije sustavno proučena. Nedostaju spoznaje o učincima kardiorespiratorne sposobnosti na inzulinsku rezistenciju u adolescenata s visokim stupnjem pretilosti, premda je broj takvih adolescenata u stalnom porastu. Ciljevi ovog istraživanja bili su ispitati povezanost kardiorespiratorne sposobnosti s inzulinskom osjetljivosti i beta staničnom funkcijom u pretilih adolescenata, osobito u onih s teškom i vrlo teškom pretilosti, te istražiti je li ta povezanost uvjetovana isključivo visceralnom pretilosti. U ovom prospektivnom, presječnom istraživanju sudjelovalo je 200 pretilih adolescenata u dobi od 10-18 godina, u kojih je uz antropometrijska mjerenja, određen sastav tijela bioelektričnom impedancijom, učinjen test oralnog opterećenja glukozom te procijenjena kardiorespiratorna sposobnost submaksimalnim testom na pokretnoj traci. Površine visceralnog i potkožnog masnog tkiva izmjerene su odgovarajućim alatima radiološkog sustava, na presječnom prikazu magnetske rezonance abdomena, u 90 pretilih adolescenata. U ispitivanoj populaciji, ustanovljena je slaba negativna korelacija između kardiorespiratorne sposobnosti i homeostatskog modela procjene inzulinske rezistencije (HOMA-IR) te slaba pozitivna korelacija između kardiorespiratorne sposobnosti i indeksa inzulinske osjetljivosti (ISI). Upotrebom univarijatne analize varijance uz Bonferroni korekciju za višestruke usporedbe, utvrđen je statistički značajan glavni učinak kardiorespiratorne sposobnosti na inzulinsku osjetljivost, poglavito uz maksimalni primitak kisika iskazan u odnosu na ukupnu tjelesnu masu. Naknadne analize pokazale su da pretili adolescenti s lošom kardiorespiratornom sposobnosti imaju značajno viši HOMA-IR te niži ISI od adolescenata s dobrom kardiorespiratornom sposobnosti. Uz maksimalni primitak kisika iskazan u odnosu na nemasnu tjelesnu masu, pretili adolescenti s dobrom kardiorespiratornom sposobnosti imali su viši oralni dispozicijski indeks od adolescenata s lošom kardiorespiratornom sposobnosti. Navedeni rezultati potvrđuju pozitivan učinak dobre kardiorespiratorne sposobnosti na inzulinsku osjetljivost i beta staničnu funkciju u pretilih adolescenata. Dvosmjernom analizom kovarijance utvrđeno je da teško/vrlo teško pretili adolescenti imaju viši HOMA-IR od blago pretilih i uz dobru i uz lošu kardiorespiratornu sposobnost. Istovremeno, HOMA-IR se nije razlikovao između teško/vrlo teško pretilih adolescenta s dobrom i blago pretilih s lošom kardiorespiratornom sposobnosti. Ovi rezultati pokazuju da na inzulinsku osjetljivost utječu i stupanj pretilosti i kardiorespiratorna sposobnost. Uz upotrebu omjera površine visceralnog masnog tkiva i kvadrata tjelesne visine kao indikatora visceralne pretilosti, serijom regresijskih analiza potvrđeno je da je povezanost kardiorespiratorne sposobnosti iskazane u odnosu na ukupnu tjelesnu masu i inzulinske osjetljivosti posredovana visceralnom pretilosti. Sveukupno, rezultati istraživanja pokazuju da je za razinu inzulinske rezistencije u pretilih adolescenata, osim stupnja pretilosti važna i kardiorespiratorna sposobnost. Stoga bi procjena kardiorespiratorne sposobnosti trebala predstavljati sastavni dio dijagnostičke obrade, a podizanje kardiorespiratorne sposobnosti važan segment terapijskog pristupa pretilim adolescentima. Obesity is associated with insulin resistance and risk of dysglycemia. Extremely obese adolescents and those with high proportion of visceral fat more often develop metabolic disorders. The association of cardiorespiratory fitness with metabolic risk in individuals with varying degrees of obesity has not been systematically studied. There is a lack of knowledge about the effects of cardiorespiratory fitness on insulin resistance in adolescents with severe obesity, although the number of such adolescents is continuously increasing. The objectives of this study were to investigate the association of cardiorespiratory fitness with insulin sensitivity and beta cell function in obese adolescents, especially in those with severe and morbid obesity, and to explore whether this association relies entirely on visceral adiposity. This prospective, cross-sectional study included 200 obese adolescents, 10-18 years of age, in which anthropometric measurements, bioelectrical impedance for body composition, oral glucose tolerance test and submaximal treadmill test for cardiorespiratory fitness assessment were performed. Visceral and subcutaneous adipose tissue areas were measured with appropriate radiological system tools on cross-sectional magnetic resonance images of the abdomen in 90 obese adolescents. In the study population, a weak negative correlation between cardiorespiratory fitness and the homeostatic model of insulin resistance assessment (HOMA-IR) and a weak positive correlation between cardiorespiratory fitness and insulin sensitivity index (ISI) was found. A statistically significant main effect of cardiorespiratory fitness on insulin sensitivity was determined by univariate analysis of variance with Bonferroni correction for multiple comparisons, especially with maximal oxygen uptake expressed relative to total body mass. Subsequent analyzes showed that obese adolescents with poor cardiorespiratory fitness have significantly higher HOMA-IR and lower ISI than adolescents with good cardiorespiratory fitness. With maximal oxygen uptake expressed relative to lean body mass, obese adolescents with good cardiorespiratory fitness had higher oral disposition index than adolescents with poor cardiorespiratory fitness. These results confirm positive effect of good cardiorespiratory fitness on insulin sensitivity and beta cell function in obese adolescents. The two-way analysis of covariance confirmed that severely/morbidly obese adolescents have higher HOMA-IR than mildly obese, with either good or poor cardiorespiratory fitness. At the same time, HOMA-IR did not differ between severely/morbidly obese adolescents with good and mildly obese with poor cardiorespiratory fitness. These results show that insulin sensitivity is influenced not only by the degree of obesity but also by the level of cardiorespiratory fitness. With the ratio of visceral adipose tissue surface area and body height squared as indicator of visceral obesity, a series of regression analyzes confirmed that the relationship between cardiorespiratory fitness expressed relative to total body mass and insulin sensitivity is mediated by visceral obesity. Overall, the results of this study show that cardiorespiratory fitness is important determinant of insulin resistance in obese adolescents, as well as the degree of obesity. Therefore, assessment of cardiorespiratory fitness should be an integral part of diagnostic procedure, while the improvement of cardiorespiratory fitness level should be an important part of therapeutic approach to obese adolescents.