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How Bariatric Surgery Results in Weight Loss
To better understand how bariatric surgery results in weight loss, it is helpful to understand how food is digested.
- The digestive process involves breaking food into simple soluble substances so tissues can absorb them.
- The process starts in the mouth when your food is mixed with salivary secretions.
- Within seconds, it travels down the esophagus in peristaltic waves to the stomach.
- The stomach normally holds about 20 to 30 oz (600-1000 cc) at one time.
- Once food enters the stomach, it is sent into the digestive tract in small increments.
- The digestive process continues in the first part of the small bowel (duodenum) where food comes into contact with bile and enzymes secreted by the liver, as well as the pancreas.
- The small bowel is where most of the absorption of food, minerals, and vitamins occurs and consists of a progression from duodenum to jejunum to ileum.
- Eventually, the unusable residue in the small bowel empties into the large bowel (colon) for excretion from the body.
Most bariatric procedures have two components that contribute to their effectiveness in contributing to weight loss:
- a restrictive component, and/or
- a malabsorptive component.
Restrictive component
During bariatric surgery a portion of the stomach is made into a small compartment bypassing the majority of the stomach. The volume of the stomach is greatly reduced. Consequently, only a limited amount of food can be eaten before a person is full and their hunger satisfied.
Malabsorptive component
Because of the anatomical restructuring that is done during bariatric surgery, the bile and pancreatic secretions that are necessary for digestion now reach the food further downstream in the small bowel. This delays the digestion of food and causes incomplete digestion and absorption. These structural and mechanical modifications allow patients to satisfy their hunger with less food that reduces caloric intake and ultimate storage of fat.
