Ghrelin is a hormone that is synthesized in the stomach. The expression and circulating levels are upregulated by fasting. Ghrelin levels are increased before meals and decreased after meals. Ghrelin is the only peripheral endogenous hormone to stimulate the appetite.
So how does this fit in with weight control? People who yo-yo diet and crash diet actually are found to do more harm than good. Ghrelin is the first hormone identified that promotes appetite. Ghrelin is secreted in the gut, where it acts as a sort of chemical room-service call to the brain for more energy.
In other words, people who try to shed pounds by depriving themselves of food through crash diets are fighting against a feedback mechanism that becomes more insistent the more weight they lose. Essentially, nobody has success with dieting.
The proper way to lose weight is very simple and basic. You must look at the energy equation which is: "energy intake versus energy output." The energy intake is regulated by hunger(which is the need for nutrients), taste (which includes incentive value) and habit (which is eating to avoid hunger), and includes sociocultural factors.
Energy output includes three major components:
- Resting energy expenditure (REE); this includes energy for basic body functions and is affected by body size, body composition, age, gender, stress, hormones, diet and training status.
- Physical activity; this includes two major components:
- Incidental exercise or unscheduled exercise, such as walking from one's car into a store
- Structured exercise, such as working out at a gym or walking on a treadmill for a set amount of time
- Thermic effect of food (TEF), this includes the energy to digest, absorb, metabolize food, and is dependent on the type of food, as well as the timing of food.
This equation represents the amount of calories one takes into one's body versus the amount of calories one is burning throughout the day. This means in order to lose weight properly one must not take in excess calories that are not going to be burned, but which will be stored as fat cells in adipose tissues. Taking in the right amount of calories will allow you to work in relation to Ghrelin. Ghrelin stimulates the appetite, which tells us we are hungry and we need fuel. Eating the proper amount of calories in relation to our bodies' needs, will allow you to take in the right amount of nutrients and calories to be used by the body rather than an excess amount to be stored as fat. This works as a positive feedback mechanism rather than a negative feedback.
