Ethnic Difference in Visceral Fat but Similar Response to Exercise in Black and White Overweight Children Catherine L. Davis, Ph.D.1 Joseph Tkacz, M.S. 1 Jerry Allison, Ph. D.2 Colleen Boyle, M.S. 1 1Georgia Prevention Institute Department of Pediatrics 2Department of Radiology Medical College of Georgia

Obesity and its Consequences Pediatric obesity is an epidemic with major implications (Strauss et al., 2001) Individuals who are obese are at a higher risk than normal-weight individuals for developing hypertension, cardiovascular disease (CVD), and type 2 diabetes (Wyatt et al., 2006) Recent research has highlighted accumulation of visceral adipose tissue (VAT) as a strong, independent risk factor for CVD and mortality (Behn et al., 2006)

Ethnic Differences in Body Fat It is widely known that Caucasians generally have greater amounts of VAT than African Americans (AA), and this has been shown in both the adult (Conway et al.,1995; Despres et al., 2000) and pediatric populations (Goran et al., 1997; Huang et al., 2001) In light of these differences, the validity of body composition measures used across ethnic groups are beginning to be questioned (Duerenberg et al., 2003)

Present Study An exercise program designed for widespread implementation should also be equally beneficial for use by children of multiple races Therefore, the goal of this study was to determine if our aerobic exercise training program, implemented to obese AA and Caucasian children, would be equally beneficial in regards to VAT reduction, despite observed differences in VAT

H1 : AA and Caucasian children will lose similar amounts of VAT after completing the P.L.A.Y. exercise program

Methods Sample consisted of 95 obese, sedentary children Recruited from local elementary schools in the Augusta area Age range 7-11 BMI Percentile >= 85 Excluded data for subjects who did not attend posttest

Methods Cont.

Table 1. Sample Characteristics Exercise Control n 68 27 Age (years) 9.5 ± 1.0 9.6 ± 1.0 BMI Z-Score 2.1 ± 0.4 BMI Percentile 97.2 ± 2.5 97.6± 2.3 Boys Girls 43% 57% 37% 63% African-American Caucasian 52% 48%

After School Exercise Program Every day after school for 15 weeks Transportation provided (school bus) Vigorous aerobic activities: walking, jogging, tag games, running games, jump rope, basketball, soccer (Gutin et al., 1999) Competition, skill deemphasized Token economy incentives for goals: Attend at least 4 days/week Average heart rate over 150 bpm each day Approximately 1 staff member per 9 children

Magnetic Resonance Imaging Visceral fat was determined utilizing a 1.5 Telsa MRI system Spin echo techniques produce T1 weighted images demonstrating good contrast between adipose and non adipose tissue While laying in the supine position, a series of 5, 1 cm wide, tranverse images were acquired beginning at the inferior border of the 5th lumbar vertebra and proceeding towards the head

Visceral fat was segmented by thresholding and quantified as adipose tissue within a region bounded by the internal-most aspect of the abdominal and oblique muscle walls and the posterior aspect of the vertebral body Values from each image will be calculated in surface area (cm2)

Results An ethnic difference on VAT was detected at baseline, where blacks < whites (t(93) = 3.1, p = .003; 3308 ± 1426 vs. 4218 ± 1418) This effect remained when age, gender, percent body fat, BMI-Z score, and waist were partialed out (p < .001, F change (1, 88) = 26.3, R2 change = 0.13). Age, gender, and BMI-Z did not contribute to the model.

Exercise reduced VAT in both high and low dose exercise groups, while controls increased (F(2, 95) = 3.5, p < 0.04; -292 ± 106 vs. -249 ± 109 vs. 101 ± 120) There was no interaction between race and group assignment on VAT change (F(2, 95) = 0.7, p =0.5

p > .05 p > .05 p > .05 p > .05