If only nourishment were a simple process: get hungry, eat, get full, stop eating. But in addition to a host of psychological factors and situational conditions, an array of biochemicals sending signals between the brain and the body control both hunger and appetite, and the difference between the two is complex. Hunger denotes a physical need for food; appetite is a desire for food—and it can be difficult to distinguish between the two. Appetite can be influenced by physical conditions, such as blood sugar levels, hormones, and exercise. It can also be influenced by moods and emotions. Stress, loneliness, and boredom can trigger eating and also drive a choice of fatty, sugary, or salty foods instead of healthier, more nutritious options. Emotional eating can also override signals of fullness, which can lead to overeating and result in weight problems if the behavior becomes routine. No one should ignore the body’s cravings, but it is wise to be mindful about what is driving a desire for food.
The Hungry Brain
It may seem like the stomach is the arbiter of hunger, but it's actually the brain that is calling the shots. it is important to remember that humans evolved under conditions of food scarcity, and scarcity prevailed for most of human history. Maintaining a body weight that allows not just for everyday functioning but for reproduction of the species has not been left to chance; many hormones and neurochemicals help regulate appetite and influence weight. Scientists believe the hormone ghrelin plays a central role in stimulating hunger. Ghrelin is produced in the stomach, and an empty stomach prompts the hormone to be released into the bloodstream and travel to the brain, where it activates nerve cells that increase appetite. Once eating begins, the stomach expands, curbing release of ghrelin and diminishing appetite..