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Childhood obesity is a significant, worldwide, public health problem. Coinciding with the increasing prevalence of obesity in youth, Type 2 diabetes has emerged as a critical health condition in this population. In the U.S. alone, approximately 215,000 U.S. youth under the age of 20 were diagnosed with diabetes, with the majority of 10-19 years old diagnosed with Type 2 diabetes. Additionally, the exact number of youth that may have Type 2 diabetes yet remain undiagnosed is unknown. Increasing physical activity to encourage weight loss among youth may reduce the incidence of Type 2 diabetes in youth; however, several recent studies reported positive associations between physical activity and components of Type 2 diabetes without weight loss in youth. These findings support previous studies in adults which observed physical activity-induced improvements in insulin dynamics without changes in body fat. The purpose of this review was to identify studies which examined the effect of physical activity without dietary intervention on markers of insulin resistance in overweight and obese youth. These studies provide strong evidence that physical activity alone, without dietary intervention, can have a positive, significant impact on insulin resistance risk and potentially prevent the development of type 2 diabetes in overweight and obese youth. The studies reviewed provide support for future interventions to shift the focus from reducing obesity to increasing physical activity for the prevention of type 2 diabetes in obese youth.

Background: Intramyocellular and intrahepatic (IHL) lipids are significantly associated with insulin resistance in adults and adolescents and may represent an early marker for developing the metabolic syndrome or type 2 diabetes., Methods: During the pilot phase of a larger cross-sectional study, we used proton magnetic resonance spectroscopy ((1)H-MRS) to determine the feasibility of noninvasively evaluating IHL in 11 male (n = 4) and female (n = 7) prepubertal children using a standard clinical system and to determine whether IHL is correlated with adiposity, fasting insulin and glucose, and liver enzymes., Results: Body mass index (BMI) (range, 13.4-32.4 kg/m(2)) and IHL stores (range, 0.07-3.2% relative to an oil phantom) were variable. IHL was correlated with body mass (r = 0.66, P = 0.037), BMI (r = 0.73, P = 0.016), percentage body fat (r = 0.73, P = 0.01, n = 10), waist circumference (r = 0.85, P = 0.016), and serum lactate dehydrogenase concentration (r = 0.77, P = 0.03) but was not significantly correlated with other markers of liver damage, including aspartate aminotransferase activity (r = 0.59, P = 0.09, n = 9) and alkaline phosphatase concentrations (r = 0.60, P = 0.087). IHL was also (P < 0.01) correlated with fasting insulin concentration (r = 0.85, P = 0.03, n = 6) and insulin resistance (r = 0.94, P = 0.006, n = 6), but these correlations were driven by the results for one child., Conclusions: These preliminary data suggest that (1)H-MRS obtained in a standard pediatric clinical environment may be used to determine IHL in healthy normal and overweight prepubertal youth. This noninvasive technique may prove useful in identifying early markers of the metabolic syndrome in at-risk youth.

Objectives: 1) Report the feasibility of completing the 180-minute Frequently Sampled Intravenous Glucose Tolerance Test (FSIVGTT) in healthy weight, overweight and obese pre-pubertal children and, 2) describe the finalized FSIVGTT protocol after addendums were implemented to decrease the frequency of mild adverse events and improve test completion rates., Methods: Insulin sensitivity was determined by FSIVGTT., Results: FSIVGTT was attempted in a total of 22 study participants. Insulin sensitivity was successfully assessed in 15 study participants (8 males, 7 females, 10 Caucasian, 4 African American, 1 Pacific Islander, age range 7-9 years). Mean insulin sensitivity was 15.1+/-9.8 (mmicro/l)(-1) min(-1) range 4.4-43.2 (mmicro/l)(-1) min(-1). However, seven study participants experienced mild adverse events of hypoglycemia. Several addendums were made to the FSIVGTT protocol to ensure study participants' comfort and safety, and to decrease the frequency of mild adverse events and increase test completion rates., Conclusions: Addendums made to FSIVGTT protocol allowed successful completion of FSIVGTT in 15 (68%) of the 22 children. These results demonstrate that FSIVGTT is challenging, yet feasible in healthy lean and obese pre-pubertal children.