Obesity is one of the most serious public health problems in the US; its prevalence has tripled in thelast three decades and is associated with a range of short- and long-term medical and psychosocial problems.Adolescence is a critical period for the development and persistence of obesity, and is associated with changesin diet, physical activity and fitness, fat distribution and insulin sensitivity. There are racial and sex-specificdisparities in the prevalence and burden of obesity. African-American (AA) females have the highest rates ofobesity, and the clustered risk factors for coronary heart disease and metabolic syndrome are twice that of AAmales. The reasons for racial and sex-specific disparities in the prevalence and burden of obesity are not wellunderstood. AA experience higher stress levels than Non-Hispanic Whites (NHW) due to economic and socialinequalities, and the effect of stress on energy-dense diet and adiposity is more prominent in females. A betterunderstanding of the mechanisms that link stress to obesity, particularly during adolescence when high rates ofobesity, increased stressful experiences and stronger behavioral and physiological responses to stress emerge,will contribute to new clinical guidelines for reducing obesity and associated medical conditions in AA females. The Physiological stress system affects obesity and mediates its adaptive functions via hypothalamic-pituitary-adrenal (HPA) axis. Prolonged stress-induced glucocorticoid secretion promotes the consumption ofenergy-dense diet (EI) and abdominal fat deposition both directly and indirectly through its effects on metabolichormones. Stress also reduces physical activity and alters energy balance. The proposed study will examinethe effects of stress and HPA axis on EI and physical activity-related energy expenditure in 100 AA and 100NHW adolescent females. The effects on EI will be assessed in two contexts, the natural environment andunder controlled conditions incorporating a standardized psychosocial stressor. Stress will be assessed in thenatural environment as multiple domains (i.e., individual, family and social), and several indices of the HPAaxis will be obtained to represent diurnal variation, its status over 12-15 weeks and reactivity to stress. Obesity-related parameters will be measured through anthropometry, fat distribution and cardio-metabolic biomarkers. Associations among stress, HPA activity/function, energy balance and obesity-related parameters will becompared between and within AA and NHW samples. In combination they will improve our understanding of thesocial factors and biobehavioral mechanisms of both racial and individual differences in obesity and facilitate thedevelopment of effective treatments within and across racial groups according to the principles of individualizedmedicine. To our knowledge, racial differences in objectively-measured diet intake and energy expenditure inresponse to stress, or their underlying physiological mechanisms, have not been assessed in adolescents oradults. This is an important knowledge gap in our efforts to develop better evidence-based translational obesityprevention and weight-control interventions as the traditional interventions are not effective with minority youth.
Obesity carries a substantial burden; and often develops in adolescence; persists into adult life and is almosttwice as prevalent in African-American women compared to Caucasian women. We will test whether African-American girls consume more sweet and fatty foods and engage in less physical activity when stressed thanCaucasians girls; and if stress hormones explain these differences. We will also test whether the differencesin diet; activity and hormones account for the higher rates of obesity in African-American girls.
