Peptide YY Is Not Sensitive to Changes in Body Weight in Non-obese Young Women

Abstract

BACKGROUND: Peptide YY (PYY) is a gastrointestinal peptide secreted from the ileum of the intestine and appears to be involved with appetite-suppression, satiety, and energy homeostasis. Fasting concentrations of PYY are altered in both anorexia nervosa and obesity. However, the role of fasting total PYY in the regulation of long-term energy balance has not been examined in healthy women. PURPOSE: The purpose of this study was to examine the long-term changes in fasting total PYY in non-obese premenopausal women following an exercise and diet program that produced weight loss, and also investigate if chronic exercise leads to changes in circulating PYY in the absence of weight loss. METHODS: All subjects were monitored for a baseline period followed by three menstrual cycles (∼3 months) during which the controlled diet and exercise intervention was implemented. Three groups were studied 1) controls (n=7) who performed no exercise, 2) exercising women who remained weight stable (n=5) and 3) exercising women who lost weight (n=10). Supervised exercise aerobic training occurred five times per week, at 70-80% of maximal heart rate, for 20 to 90min as the study progressed. Subjects were fed a controlled diet comprised of 55% carbohydrates, 30% fat, and 15% protein. Body composition, resting metabolic rate (RMR), and fasting total PYY concentrations were measured pre- and post-intervention. RESULTS: Body weight (p<0.001), fat mass (p<0.001), and RMR (p=0.020) decreased in the weight-loss exercise group (-3.2±0.8kg, -2.6±0.7kg, -43kcal/day, respectively), but did not change in the control group or weight-stable exercise group. Change in VO2max was significantly greater in the exercising groups (20.6±8.9%) compared with controls (11.8 ± 9.2%). Fasting PYY did not change (p>0.05) with exercise training and weight loss (20.1±3.5pmol/L and 20.1±7.45pmol/L, pre and post PYY, respectively), or exercise alone (20.3±2.0pmol/L and 23.0±5.0pmol/L, pre and post PYY respectively). CONCLUSIONS: Fasting total PYY does not appear to play a key role in the regulation of energy balance during a combination of diet and exercise, nor does it appear to play a role in the adaptive changes associated with training in the absence of weight loss. Supported by NIH Grants 1R01HD39245-01A1 and M01 RR 10732.