What can cause hunger if the stomach is removed?

Hunger can be influenced by hormonal changes, even if the stomach has been removed. The body regulates hunger through a complex interplay of hormones, such as ghrelin, leptin, and insulin. Ghrelin, often referred to as the "hunger hormone," is produced in the stomach and signals the brain to stimulate appetite. When the stomach is removed, the levels of ghrelin may be altered, affecting the sensation of hunger. The body also compensates for the absence of the stomach by adjusting the release of other hormones that contribute to hunger and satiety, leading individuals to still experience hunger signals despite the lack of a stomach.

In contrast, the other factors mentioned—stomach contractions, lifestyle factors, and food odors—are either directly linked to the physical structure of the stomach or dependent on contextual influences that may not apply universally to individuals without a stomach. For example, without the stomach to contract, mechanical cues like stomach fullness are eliminated, directly impacting the sensation of hunger that relies on such contractions. Similarly, lifestyle factors and food odors can influence appetite but do not inherently cause hunger independent of the hormonal regulatory processes. Thus, hormonal changes provide the most relevant explanation for hunger signals in individuals who have undergone a gastrectomy or similar