Our major unifying hypothesis is that diets comprised of high sugar, energy dense, low fiber meals, are associated with a post-prandial metabolic, hormonal and psychosocial profile that promotes overeating and sedentary behavior. Specific Aims: (1) Compare the effects of a HIGH SUGAR, LOW FIBER (HSLF) meal versus a LOW SUGAR, HIGH FIBER (LSHF) meal on insulin dynamics, selected gut peptides, mood and levels of physical activity in minority adolescents, (2) Explore the effects of HSLF versus LSHF meals on post-prandial ad libitum food intake, (3) Explore differences in reaction to HSLF versus LSHF meals in lean and overweight adolescents and (4) Examine ethnic differences in meal responses between Hispanic and African American children. Research Design and Methods: We will employ a cross-over design with a 3-4 week washout period where normal weight and overweight African American and Hispanic youth come to our Observation Lab in a fasting state and consume high sugar and low sugar meals at separate visits in random order. Meal consumption will be followed by five hours of intensive observation in which we quantify real-time physical activity in laboratory setting that was designed to offer equally attractive choices for active or sedentary behaviors. After 5 hours, participants will be offered food platters with an array of food types and be invited to eat ad libitum. Subsequent energy and nutrient intake will be quantified. Rationale: This study is prompted by three observations: (1) The disproportionate levels of obesity and risk for type 2 diabetes and cardiovascular disease in Hispanic and African American children; (2) The rapid decline in physical activity during puberty especially in Hispanic and African American adolescents, and (3) Children, and particularly minority children, tend to have diets high in added sugars and low in fiber. Thus, it is imperative to improve our understanding of the interrelationships between dietary intake, physical activity and risk factors for type 2 diabetes and cardiovascular disease in minority youth, particularly during puberty, when physical activity levels significantly decline. Relevance to public health: This study will provide new information on the acute effects of meal composition on mood and subsequent choices of physical activity in normal weight, healthy overweight and insulin resistant overweight Hispanic and African American youth. Furthermore, we suggest that our findings may potentially lead to a better understanding the acute affects of poor nutritional choices on physical activity in minority adolescent populations at high risk for obesity, diabetes type 2, and other obesity-related diseases.