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Do We Really Need 20 Minutes to Feel Full?

There is a time gap between when enough food has been eaten to satisfy hunger and when the brain actually realizes fullness. Why?

Sitting down to dinner with a rumbling stomach often leads to finishing the meal in record time. However, about half an hour after clearing the plate, an uncomfortable fullness may be felt, as if the stomach could pop.

There is often talk about a lag between taking the first bite and satisfying hunger, with a common belief that this time delay lasts around 20 minutes. But exactly how long does it take for the brain to register fullness?

On average, it takes about 20 minutes for the body to send signals to the brain indicating enough food has been consumed. However, the exact duration of this lag depends on various factors, including the type of food consumed and typical eating habits, according to Dr. Nina Nandy, a gastroenterologist based in Texas and spokesperson for the American Gastroenterological Association.

This is because the brain relies on several different mechanisms to determine fullness.

Dr. Nina Nandy

Feelings of hunger and fullness, or satiety, are largely controlled by hormones, particularly ghrelin, an appetite-stimulating hormone produced in the gut, and leptin, an appetite-suppressing hormone released by the body’s white fat cells. Ghrelin fluctuates during eating and fasting, while leptin levels remain fairly steady. Additional hormones, such as PYY and GLP-1 from the gut and insulin from the pancreas, have also been shown to increase feelings of fullness after eating.

The brain also regulates hunger based on information from nerves that sense when the stomach gets stretched, as well as signals from taste buds and smell receptors.

“When these signals collectively indicate that enough has been eaten, the brain reduces the desire to eat further.”

Dr. Nina Nandy.

However, a roughly 20-minute delay exists due to the time needed for the body to adjust its production of hunger-related hormones, which travel more slowly via the bloodstream compared to nerve impulses. Electrical signals from the gastrointestinal tract travel along nerves at lightning speed, reaching the brain almost instantly. Hormones, on the other hand, travel via the bloodstream.

The time it takes for the body to generate satiety signals and send them to the brain also depends on the type of food consumed. Foods high in fiber, such as fruits, vegetables, and whole grains, tend to promote satiety, while low-fiber, processed foods delay the feeling of fullness, according to Dr. Nina Nandy. This is because fiber helps switch off the production of ghrelin, trigger the secretion of appetite-suppressing gut hormones, and exert pressure on the stomach’s stretch receptors, as noted in a 2022 review published in the journal Critical Reviews in Food Science and Nutrition.

Eating habits also influence satiety after meals. Eating slowly gives the body more time to signal fullness, while paying attention to food and savoring every bite can help better tune into these signals, a concept known as mindful eating, according to Dr. Nandy. Thoroughly chewing food may also boost satiety by increasing sensory feedback to the brain, as indicated in a 2018 meta-analysis published in the journal Appetite.

Certain medical conditions, such as hypothyroidism and diabetes, can disrupt satiety signals by slowing down the passage of food through the stomach, causing prolonged feelings of fullness. The diabetes drug Ozempic and weight-loss drug Wegovy partially work by slowing down the rate that food empties from the stomach.

Leptin resistance, a condition in which the amount or effect of this satiety hormone decreases, can cause persistent hunger. This condition can lead to obesity by promoting excessive food intake and often arises from rare genetic mutations, as was the case with two siblings experiencing intense, insatiable hunger.

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