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Carter wins Poster Award at Center for Exercise Medicine Second Annual Symposium

October 4, 2014

Stephen Carter

Stephen J. Carter, PhD, ACSM-CPT, postdoctoral fellow in the Department of Human Studies, School of Education, and in the Nutrition Obesity Research Center (NORC), was one of three Poster Award winners at the UAB Center for Exercise Medicine Second Annual Symposium, Focus on Exercise Biology in Medicine and Rehabilitation, held on September 26, 2014 for his abstract titled "Racial Differences in Erythropoietin and Hemoglobin Before and After Weight Loss in Women."

African American (AA) women often exhibit dissimilar sex hormone characteristics and lowered hemoglobin compared with European American (EA) women. While weight loss has previously been shown to reduce androgenicity, it remains unclear how such changes may influence hemoglobin concentrations in overweight premenopausal women.

In this study, a mixed-race cohort of 64 overweight (body mass index, or BMI, of 28.3 plus or minus 1.4 kg/m2), premenopausal women were provided a standardized 800 kcal/day diet for the purpose of reducing body mass index (BMI, less than 25 kg/m2).

Participants were randomly assigned to engage in either diet only or diet and supervised aerobic exercise sessions three times per week. Physiological measurements and blood sampling were performed at baseline and following a two week weight stabilization period once the target BMI was reached.

Data was pooled as differences did not emerge between diet only and diet plus exercise. Baseline measures indicated significant differences between races, as AA women had lower hemoglobin (AA, 11.6 plus or minus 0.9 g/dL versus EA, 12.5 plus or minus 0.8 g/dL; P less than 0.05) and higher erythropoietin, or EPO, (AA, 14.3 plus or minus 9.8 mIU/mL versus EA, 7.9 plus or minus 2.4 mIU/mL; P less than 0.05) compared with EA women. Following weight loss, hemoglobin levels were lowered in both races (AA, 10.9 plus or minus 1.1 g/dL versus EA, 12.1 plus or minus 0.9 g/dL; P less than 0.05), while EPO increased (AA, 24.2 plus or minus 24.7 mIU/mL versus EA, 8.6 plus or minus 4.9 mIU/mL, P less than 0.05). Changes in hemoglobin from baseline to weight loss were negatively associated with the change in EPO (r equals -0.717; P less than 0.05) and positively with testosterone (r equals 0.329; P less than 0.05).

Dr. Carter and fellow researchers concluded, for the first time, that weight loss lowers hemoglobin independent of race and that despite having higher EPO levels AA women exhibit lower hemoglobin. The team recommends that strategies are needed to clarify the appropriate caloric deficit during weight loss to prevent the unintended consequence of lowering hemoglobin concentrations.

Dr. Carter’s research interests include the therapeutic potential of hypoxic exposure for the treatment of obesity and related comorbidities, cutaneous microvascular and endothelial function in health and metabolic disease, and cardiovascular and metabolic responses to exercise in heat and cold. His mentors are Professor Gary R. Hunter, PhD, and assistant professors Gordon Fisher, PhD, and Eric P. Plaisance, PhD.