Randomized Controlled Trial to Improve Adiposity, Inflammation, and Insulin Resistance in Obese African-American and Latino Youth

The purpose of this study was to examine ethnic differences in the metabolic responses to a 16-week intervention designed to improve insulin sensitivity (SI), adiposity, and inflammation in obese African-American and Latino adolescents. A total of 100 participants (African Americans: n = 48, Latino: n = 52; age: 15.4 +/- 1.1 years, BMI percentile: 97.3 +/- 3.3) were randomly assigned to interventions: control (C; n = 30), nutrition (N; n = 39, 1x/week focused on decreasing sugar and increasing fiber intake), or nutrition + strength training (N+ ST; n = 31, 2x/week). The following were measured at pre-and postintervention: strength, dietary intake, body composition (dualenergy X-ray absorptiometry/magnetic resonance imaging) and glucose/insulin indexes (oral glucose tolerance test (OGTT)/intravenous glucose tolerance test (IVGTT)) and inflammatory markers. Overall, N compared to C and N+ ST reported significant improvements in SI (+ 16.5% vs. -32.3% vs. -6.9% respectively, P < 0.01) and disposition index (DI: + 15.5% vs. -14.2% vs. -13.7% respectively, P < 0.01). N+ ST compared to C and N reported significant reductions in hepatic fat fraction (HFF: -27.3% vs. -4.3% vs. 0% respectively, P < 0.01). Compared to N, N+ ST reported reductions in plasminogen activator inhibitor-1 (PAI-1) (-38.3% vs. + 1.0%, P < 0.01) and resistin (-18.7% vs. + 11.3%, P = 0.02). There were no intervention effects for all other measures of adiposity or inflammation. Significant intervention by ethnicity interactions were found for African Americans in the N group who reported increases in total fat mass, 2-h glucose and glucose incremental areas under the curve (IAUC) compared to Latinos (P's < 0.05). These interventions yielded differential effects with N reporting favorable improvements in SI and DI and N+ ST reporting marked reductions in HFF and inflammation. Both ethnic groups had significant improvements in metabolic health; however some improvements were not seen in African Americans.