Detection of exercise energy expenditure.

Introduction. To understand how energy intake is related to energy expenditure, we hypothesized that (1) exercise energy expenditure (EEE) is not consciously detected or compensated for through increased food intake in response to variation in circulating metabolic fuels (Studies one and two), and is unaffected by hormones signaling hunger (total ghrelin), satiation (CCK), and satiety; and (2) increases in exercise intensity suppress appetite in a dose-dependent fashion related to increases in secretion of epinephrine (E) and norepinephrine (NE) (Study three). Methods. Ten postmenopausal women served as their own controls in each study. In Study one, they walked two hours on the treadmill (365 Kcal) twice, either 1 h before or 1 h after the 1000 and 1700h meals, with altered concentrations of metabolites and hormones. In Study two, exercise either reduced energy balance by 430 Kcal or a 400 Kcal intravenous nutrient infusion restored it. In Study three, EEE was 525 Kcal twice in a day at intensities of either 40% or 80% of peak effort. Appetite, metabolism, and concentrations of hormones and metabolites were measured. Ad libitum meals at mid-day (Study two) or end of the day (Study three) tested feeding compensation. Effects of trials and time were analyzed with two-way mixed model ANOVA using averages and areas under the curve during exercise and periods of nutritional manipulation. Results. Appetite was suppressed to the same extent during late morning and afternoon exercise in all three studies. Appetite suppression during exercise, and equal appetite ratings immediately before and after the meals, were unrelated to difference in circulating metabolites or hormones (Studies one and two), energy balance (Studies one and two), or exercise intensity (Study three). There also was no compensatory increase in food intake in studies two and three. Conclusion. EEE is not consciously detected within one day of exercise. Control of appetite and feeding does not respond to EEE or metabolic and hormonal changes associated with changes in energy balance or exercise intensity. Other, possibly neural and circadian controllers probably influence meal taking after exercise.Ph.D.Biological SciencesPhysiologyPsychobiologyPsychologySocial SciencesWomen's studiesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/126980/2/3287658.pd