This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The goal of this research study is to gain a better understanding of how calories expended during exercise or caloric restriction affect our appetite and food consumption. Rapid growth in the incidence of obesity in the United States and other developed countries has increased the need for a more efficient use of exercise and diet in efforts to prevent or reverse obesity.In this study we will try to answer two questions: (1) Do calories that are eaten have the same effect on our sense of hunger and satiety as the same number of calories delivered directly into the blood? To answer this question, we will compare appetite and satiety produced by food eaten during a meal to the same number of calories introduced by intravenous injection. Our guess is that only calories that we ingest by mouth and digest through our gastro-intestinal tract will affect our sense of hunger and satiety. (2) Do calories that are expended during exercise have the same effect on our sense of hunger and satiety as the same number of calories withheld from a meal? To answer this question, we will compare appetite and satiety resulting from two hours of exercise to the same number of calories withheld from a meal. Our guess is that calories that are expended during exercise do not affect our sense of hunger and satiety, but that the calories withheld from a meal, do. Besides measuring the levels of hunger, desire to eat, the estimate of capacity to eat, and the sense of fullness, we will measure several hormones in the blood samples that will be withdrawn approximately every 30 minutes during 12 hours of daytime. Some of these hormones are thought to signal hunger and satiety, and others are released when our body detects reduced availability of energy. We also will measure energy metabolism by sampling consumption of oxygen and production of waste gas, carbon dioxide. A better understanding of how calories expended during exercise or caloric restriction affect our appetite, and food consumption affects our satiety, will help us develop better strategies for using exercise and food restriction to prevent obesity or induce weight loss.
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