The obesity of the child and the adolescent is executed with adult obesity, especially it is to become known that obesity of the adolescent compared with obesity of the child have more increased risk to be adult obesity. It has been reported that long-term exercise training improve on the body weight and body composition and as physical activity increase, it has positive effect in weight loss, improvement of physical fitness and prevent of disease (Forbes, 1991).

The energy expenditure according to the exercise is used by the ratio of 6 : 4 at the primary use of glucose and lipid. However, the use of lipid increase more than glucose after 20 minutes. Therefore, it has been reported that training over 30 minutes is useful for the improvement of body composition (ACSM, 1995). Inadera et al (1993) reported that the accumulation of visceral fat was a more harmful risk of complication than subcutaneous fat. Visceral fat and subcutaneous fat have been found to have different biological and molecular characteristics. Owens et al (1999) reported that aerobic training (157 beats/min, 40 min/set, 5 times/week, for 4 months in obese adolescents) decreased subcutaneous fat by 16.1%. Mourier et al (1997) investigated the effects of aerobic training on body composition by having obese subjects exercise at 75% of V0₂max over 45 minutes, 2 days a week, for a period of 8 weeks. Data indicated that abdominal subcutaneous fat and visceral fat were decreased by 18% and 48%, respectively.

Data from the current study indicate that this training significantly decreased body weight (4.7kg), BF% (9.2%) and increased LBM (1.19kg). Also, abdominal subcutaneous fat and visceral fat were decreased, while the rate of VFV/SFV, used as an index of abdominal obesity, tended to decrease in the aerobic exercise group and significantly increased in the control group. These results are in agreement with those of some previous experiments (Owens, 1999; Mourier, 1997).

In addition, Hotamisligil (1993) reported insulin resistance is a result of accumulation of visceral fat, which is also associated with high morbidity due to increased incidence of atherosclerosis. Also, compared with subcutaneous fat, visceral fat has a steady state of plasma glucose (SSPG) and has increased insulin resistance (Yamashita, 1996). This study showed that a reduction in abdominal visceral fat due to engagement in aerobic exercise was responsible for a reduction in insulin concentration, which in turn improved insulin resistance.

Prospective studies have recognized that high blood pressure and obesity are related to the degree of aortic atherosclerosis (Berenson et al., 1992). The clustering of atherosclerotic risk factors in early adult life is associated with cardiovascular disease in middle-aged men (Mahoney et al., 1996). However there are conflicts about the early onset of atherosclerosis in children. Because fatalities due to cardiovascular disease rarely occur in children and young adults, it is hard to define atherosclerotic risk patterns for children in tissue studies. From the postmortem studies, the characteristics of atherosclerotic lesions in adolescents are similar to those in adults (Kwiterovich, 1993; PDAY Research Group, 1990). Dyslipidemia, such as high low density lipoprotein cholesterol (LDL-C) and low high density lipoprotein cholesterol (HDL-C), is significantly associated with the severity of the atherosclerotic lesion in children and early adulthood (Mahoney et al., 1996). Yet, it is of interest to associate dyslipidemia with left ventricular (LV) mass in a population at increased risk of acquiring cardiovascular disease. LV hypertrophy, determined by echocardiography, has been recognized as being strongly associated with cardiovascular diseases (Levy et al., 1989; de Simone et al. 1992). The Framingham Heart Study found a six- to eight-fold increased risk of cardiovascular events for individuals with LV hypertrophy in adults (Kannel et al., 1987). Previous studies had reported that, in young adolescents, LV hypertrophy was associated with higher blood pressure, obesity and genders (Goble et al., 1992). Echocardiography has been recommended as the optimal screening tool for diagnosis of LV hypertrophy (Reichek & Devereux, 1981; Savage et al., 1987). The index of obesity, such as high body mass index and WHR, has been related to increased LVmass in the adult population. Kono et al. (1994) also found that obesity is closely related to LVmass in Japanese children. Eisenmann et al. (2000) demonstrated that cardiac dimensions were not related to habitual physical activity in a free-living population of 9 - to 18-year-old Quebec subjects; they appear to be primarily determined by normal growth and maturation. These results are consistent with the conclusions of Blimkie et al. (1980), who reported that the seemingly good relationship between cardiac dimensions and aerobic capacity is mainly attributable to the shared influence of body size on both of those factors. In this study, despite producing favorable changes in aerobic capacity, there was no evidence that the 24-week aerobic exercise program produced any favorable changes in LV structure, as compared with the control group. It is also reasonable to assume that genetic and other environmental factors contribute to cardiac dimensions (Bouchard & Lortie, 1984). It has been estimated that 30-70% of heart size and cardiac function phenotypes, as assessed by echocardiography are due to inherited traits (Bouchard et al., 1997).

In sum, visceral adipose tissue was associated with unfavorable LV structure and function. However, despite producing favorable changes in aerobic capacity and general and visceral adiposity, we did not provide evidence that the 24-week aerobic exercise produced favorable changes in LV structure compared with the control group. Thus, interventions that are last longer than 24 weeks, and/or produce greater changes may be required to elicit appreciable effects. In other words, visceral adiposity may be necessary before significant favorable effects on obesity-associated LV variables can be seen in obese youths.