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Satiety (suh-TIE-ity) is the condition of being full. Set-point theory cannot explain why we stop eating at a particular meal, because we stop eating well before the fat enters our cells. Rat research suggests that satiety signals arise from the stomach.

What is satiety? What causes satiety?

Deutsch, Young, and Kalogeris (1978) implanted a tube below the stomach in rats. They siphoned off milk as the rats drank it, so the milk never reached the large intestine. Instead of drinking more than usual, the rats drank the same amount as usual. The arrival of milk in the stomach was apparently enough by itself to generate the "satiety signal" that shut off hunger.

This kind of research, showing that a full stomach led to a feeling of fullness or satiety, led to development of a weight-loss device called the gastric bubble. The gastric bubble was a small plastic balloon inflated in a patient's stomach. The balloon occupied space in the stomach, leading to feeling of "fullness" after relatively little eating.

A gastric bubble

What treatment is used now, instead of the gastric bubble?

The gastric bubble proved to cause complications in some patients, and it deteriorated after a time. Researchers started turning their attention toward a more permanent approach: reducing the size of the stomach. This could be accomplished by stapling the stomach, fitting it with a constricting band, stimulating it with mild electric current, or surgically removing part of the stomach or large intestine. All of these approaches have been tried with obese people with more or less success.

After stomach reduction surgery, a person feels full quickly after starting a meal and must keep portions small. For most people, this results in rapid and permanent weight loss. However, a determined eater can defeat the operation by constantly eating small amounts. Weight loss is not automatic, even after surgery.

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