Background: \nYoung adult Mexican Americans (MA) exhibit lower insulin sensitivity (Si) than nonHispanic whites (NHW), even when controlling for fitness and adiposity. It is unclear if MA are as responsive to the same lifestyle intervention as NHW.\nObjective: \nWe developed a model to examine cardiometabolic plasticity (i.e., changes in Si and plasma lipids) in MA compared to NHW adults in response to a diet-exercise intervention.\nDesign: \nSedentary subjects (20 NHW: 11F, 9M, 23.0 y, 25.5 kg/m2; 17 MA: 13F, 4M, 22.7 y, 25.4 kg/m2) consumed their habitual diets and remained sedentary for 7 days, after which fasting blood samples were obtained, and a 3-h intravenous glucose tolerance test (IVGTT) was performed with the insulin area under the curve (IAUC) used to estimate Si. Subjects then completed a 7-day diet/exercise intervention (diet: low saturated fat, low added sugar, high fiber; exercise: cycling, six total\nsessions lasting 40ââ?¬â??45 min/session at 65% VO2 max). Pre-intervention tests were repeated.\nResults: \nPre intervention IAUC was 28% higher (p,0.05) in MA (IAUC pre = 2298 mU*180 min/mL) than in NHW (IAUC = 1795 mU*180 min/mL). Following the intervention, there was a significant reduction in IAUC in MA (29%) and NHW (32%), however, the IAUC remained higher (p,0.05) for MA (post = 1635 mU*180 min/mL) than for NHW (post = 1211 - mU*180 min/mL). Pre test plasma lipids were not different in MA compared to NHW. Plasma cholesterol and TG concentrations significantly improved in both groups, but concentrations of low density lipoprotein-cholesterol and small dense LDL particles significantly improved only in the NHW.\nConclusion: \nWith a short-term diet-exercise intervention, the magnitude of improvements in Si and serum cholesterol and TG in Hispanics are similar to those in NHW. However, because at the outset MA were less insulin sensitive compared to NHW, within the short timeframe studied the ethnic gap in insulin sensitivity remained.
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