Journal Title (Medline/Pubmed accepted abbreviation): Int. J. Sport Nutr. Exerc. Metab.
Summary of Background and Research Design
Background:Visfatin is an adipocytokine produced by many tissues, including visceral body fat cells. Visfatin may increase insulin resistance. It has been shown that exercise reduces visfatin levels in adults, but not artificial weight loss (from gastrectomy). It is unknown whether it is the exercise itself or the reduction in body fat that led to lower plasma visfatin concentrations. It is also unknown whether these observations hold true in adolescents.
Hypothesis/Research Question: Do obese adolescents have higher visfatin levels than healthy weight counterparts? Does aerobic exercise reduce plasma visfatin and/or insulin resistance in obese adolescents?
Subjects:Female Korean high school students that do not regularly exercise were recruited.20 nonobese participants (age 16.72 ± 0.69 yrs, BMI 19.48 ± 1.72 kg/m 2 ) and 18 obese (as defined by the authors) adolescents (age 16.96 ± 0.89 yrs, BMI 28.02 ± 1.89 kg/m 2 ) were enrolled.
Experimental design: Obese individuals were randomly assigned to two independent groups- aerobic exercise or no exercise.
Treatments and protocol:The exercise group exercised 4 days/wk for 12 wks. Each session consisted of 5 min warmup, 30-40 min of jumping rope beginning at 40% of the observed maximal heart rate and gradually increasing to 60-80% of the max heart rate, and then 5 min cool down. Each session burned 300-400 kcal.
Blood was drawn before the first session and 48 hrs after the last aerobic session to assess plasma total cholesterol, HDL cholesterol, triglycerides, glucose, and visfatin.
Summary of Research Findings
- The obese group all had significantly higher measurements for obesity-related factors (waist circumference, plasma triglycerides, etc.) than the nonobese group.
- Despite the fact that dietary intake did not change from pre- to post-training in either the exercise or the control group, there was significant weight loss in the exercise group.
- After 12 wks of aerobic training, visfatin, insulin, and insulin resistance were significantly reduced in obese adolescents. In the non-exercising group, these values were either unchanged or worsened.
Interpretation of findings/Key practice applications:
Because the exercise program created weight loss, it was not clear from this study whether the decreases in visfatin, insulin, or insulin resistance were due to weight loss or to the exercise itself. However, the aerobic exercise program, even in the absence of caloric restriction, caused significant reductions in risk factors for chronic disease and should be recommended for overweight or obese adolescents.