Zoo 251: Chapter 26- body weight and energy balance & appetite 

• weight is determined by one's energy balance- if energy intake and output are equal, body weight is stable
• if intake exceeds output - weight gain
• output exceeds intake - weight loss 
• SHORT-TERM REGULATORS OR APPETITE:
  • Ghrelin- secreted by parietal cells in the gastric fundus, esp. when stomach empty 
    • produces sensation of hunger and stimulates the hypothalamus to secrete growth hormone-releasing hormone, priming the body to take advantage of the nutrients about to be absorbed
    • within an hour after eating, ghrelin secretion ceases 
  • Peptide YY (PYY)- secreted by enteroendocrine cells in the ileum and colon, which sense that food has arrived even as it enters the stomach