Gastric sleeve surgery, also known as sleeve gastrectomy, reduces the stomach’s size. This procedure transforms the stomach into a smaller, tube-shaped pouch, helping individuals achieve significant and sustained weight loss. It is offered to those with substantial obesity who may also have related health conditions.
Physical Restriction of Food Intake
Gastric sleeve surgery significantly reduces the stomach’s capacity. During the procedure, surgeons remove approximately 75% to 85% of the stomach, leaving a narrow, tube-like stomach. The remaining stomach can hold a much smaller amount of food, directly limiting calorie intake at each meal.
Patients feel full much faster after this surgery. The reduced volume means only a few ounces of food can be consumed before satiety signals are triggered. This physical restriction makes it difficult to overeat, leading to a natural decrease in overall food consumption. The smaller stomach also contributes to a prolonged feeling of fullness, reducing the urge to snack between meals.
Hormonal Shifts and Appetite Control
Beyond physical restriction, gastric sleeve surgery brings about profound hormonal changes that influence appetite and metabolism. A significant portion of the stomach, specifically the fundus, is removed during the procedure. This part of the stomach is where most ghrelin, often called the “hunger hormone,” is produced.
The removal of the fundus leads to a substantial decrease in ghrelin levels in the bloodstream. Lower ghrelin concentrations reduce feelings of hunger and cravings for food. This hormonal alteration is a key reason why many patients experience a significant reduction in appetite after surgery, making it easier to adhere to smaller portion sizes.
The altered passage of food through the digestive system also impacts other gut hormones. Food reaches the lower parts of the small intestine more quickly, stimulating the release of satiety-promoting hormones like Glucagon-Like Peptide-1 (GLP-1) and Peptide YY (PYY). These hormones enhance feelings of fullness and satisfaction after eating. Increased GLP-1 also plays a role in glucose metabolism by stimulating insulin secretion, contributing to improved blood sugar control.
Metabolic Improvements Beyond Calorie Restriction
Gastric sleeve surgery offers metabolic benefits that extend beyond simply eating less and feeling full. Many patients experience rapid improvements in conditions such as type 2 diabetes, often even before substantial weight loss has occurred. This suggests that the surgery triggers complex physiological changes that directly impact metabolic health.
One concept explaining these rapid metabolic shifts is the “hindgut hypothesis.” This theory proposes that the faster delivery of nutrients to the distal (lower) small intestine enhances the release of beneficial hormones like GLP-1 and PYY. These hormones improve insulin sensitivity and glucose metabolism, leading to better blood sugar control.
The procedure also influences the gut microbiome, the vast community of microorganisms residing in the intestines. Bariatric surgery can alter the composition and diversity of these bacteria, often shifting towards a healthier profile. Changes in the gut microbiota can positively impact metabolism and weight regulation. These microbial changes can influence energy extraction from food and affect metabolic pathways, further contributing to the overall effectiveness of gastric sleeve surgery in promoting weight loss and improving related health conditions.