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Gastric bypass or bariatric surgery is a major surgical procedure which can be hazardous and associated with serious complications. It is therefore seen as the last resort in a person’s battle to reduce weight, when conventional dieting and exercise has not been successful. To be considered for the procedure, people must exceed a certain body mass index (usually 40 or more) or have a medical or physical condition seriously affected by their excessive weight.
What is gastric bypass surgery?
The procedure consists of reducing the size of the stomach to that of an egg (it’s normally about the size of a closed adult fist). The part of the intestine immediately after the stomach is usually bypassed during the procedure, making the gut shorter and limiting absorption of nutrients from digested food.
Effect of bariatric surgery
The primary intention of the surgery is to physically restrict the quantity of food which people can eat at any one time, to prevent over-eating. Bypassing the part of the gut where most absorption of nutrients takes place also helps reduce weight by limiting the calorific (energy) value of food eaten.
Is it effective?
In some people it’s so effective that they start to lose weight immediately and weight-related conditions, such as diabetes, have been known to improve before any weight has been lost. Some people find it no problem adjusting their food intake following surgery, despite a lifetime of over-eating, and lose weight easily.
It’s our brains which tell us when to stop eating
It has been known for a long time that eating behaviour is controlled by complex interaction between hormones and nerves acting between the stomach and brain. We all know that when our stomach is empty our brains tell us to eat something and it makes sense that conversely when we eat a good meal our brains shut down our desire to eat more.
More recent research has partly uncovered the particular parts of the brain, nerve pathways and hormones involved. It has been found that nerve signals are sent to the brain from the stomach in response to food.
It’s thought that the signal to stop eating is given in response to the calorific value of the food being absorbed. If the calorific value is low more food is consumed before the signal is given.
Clearly these signals are important to guide our eating – so that we eat sufficient but do not eat too much at a time. (It is thought that if there is too much food in the stomach it is not absorbed properly).
We can, of course, choose to ignore those signals to stop eating if we wish. But in the case of obese people it appears that those signals are very weak or absent, making it difficult for them to know when they should stop eating.