A. Limbic system: Responsible for memory and emotions. Processes information about previous experiences with food and reward. Could encourage someone to eat more or less.
B. Hypothalamus: Processes signals from gut hormones and fat, and sends its own signals. These include agouti-related protein, MCH and NPY, which block pain signals, give a calming effect and stimulate feeding. There are also other signals, such as MSH, which suppress appetite. The balance of all of these will determine a person’s appetite.
C. Vagal afferents nerve: Sends messages from the gut to the brain stem.
D. Your genes: Can affect how any of these hormones work – a variation could alter a person’s appetite to eat more or less.
E. Stomach: Secretes hormones like ghrelin, which tells you that you are hungry.
F. Pancreas: Secretes several hormones, including insulin, incretins and amylin, which tell you to eat less.
G. Duodenum: Part of the intestines that produces GLP1 and CCK, which send signals that tell you to eat less.
H. Intestines: Secrete a hormone called PYY 3-36, which tells the hypothalamus to suppress appetite.
I. Fat tissue: Secretes leptin, a powerful hormone that acts on the hypothalamus and is responsible for long-term inhibition of food intake.
J. Environmental factors: Increased marketing and availability of food, particularly high-calorie, processed foods.