How Does Your Stomach Tell Your Brain That You're Full?

Man eating a salad
A variety of signals from your body tell your brain when your stomach is full. (Image: Minerva Studio/iStock/Getty Images)

Satiety, the sensation that you've had enough to eat, results from a balance of hormonal and neurological signals reaching your brain from your stomach. Other factors, such as the sensory quality of food, also contribute to satiety. Scientific research has revealed much about this mysterious function and how it contributes to weight control, but much remains to be learned.

Feedback Mechanisms

Hunger and satiety -- the feeling of fullness that tells you to stop eating -- are complex functions regulated by numerous feedback mechanisms in your body. One of those signals comes from your stomach wall stretching to accommodate the meal you are eating. Nerve stretch receptors send signals to the brain that the stomach is expanding and you can begin to taper off and stop eating. At the same time, a hormone called ghrelin, produced when your stomach empties to trigger a hunger message, starts to decrease. The result is more impulses reaching your brain saying to stop eating than to start or continue eating.

Timing

It takes about 20 minutes after you start eating for the message to stop eating to form and reach your brain, says registered dietitian Joanne V. Lichten, Ph.D., author of the book "Dining Lean - How to Eat Healthy When You're Not at Home." If you are a speedy eater, it may serve you well to cultivate a slower pace for dining. Other benefits of eating slowly include savoring the taste of your food, which by itself promotes mental and emotional satiety from eating, and improved digestion. Lichten also suggests you can test to see if you are full by standing up at some point during your meal and sensing how your stomach feels. If you feel comfortable but not over-full when you stand, then you've eaten enough. By doing this you will avoid the sensation that often occurs at the end of a meal, when you stand up and realize from the bloated feeling in your stomach, that you've overindulged.

Cholecystokinin

A hormone produced by your digestive system, called cholecystokinin, signals your brain when you've eaten. More is released in a large meal and less from a small snack. When you are dieting to lose weight, your stomach counterbalances the reduced food intake by cutting back on the amount of this hormone it will release, encouraging you to eat more and go off your diet. Loading up on fiber will help you circumvent this built-in survival tool.

Children's Weight Issues

If you are raising children and want to help them maintain their healthiest weight, the American Dietetic Association advises not to encourage them to clean their plates. Instead, watch for signs of fullness, such as restlessness at the table or playing with food. Allowing your child to leave the table when she has signalled that she has eaten enough will work in your child's favor by avoiding food aversions and overeating.

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