PYY and Anorexia: Weight loss might also be due to decreased energy intake and increased energy expenditure during exercise as recent evidence suggests that high-intensity activity could by regulating downstream signaling pathways of hunger hormones and upstream signaling pathways of satiety hormones (PYY) alter appetite (by altering appetite-regulating hormones, including PYY) and limit energy intake as an exercise-induced anorexia (41, 44).