Bariatric surgery for weight loss: is it possible?

Not everyone who is obese can lose weight through diets, exercise and psychotherapy. Some people therefore consider bariatric surgery. With a sleeve gastrectomy or a gastric bypass, parts of the stomach are separated. It’s worth noting that even those who decide to have bariatric surgery also have to change their eating habits.

Bariatric surgery is an option for people with severe obesity. This means those with a body mass index (BMI) of 35 kg/m² or higher.

In Switzerland, two methods are predominantly used: gastric bypass and sleeve gastrectomy. Both cause the patient to experience reduced hunger and appetite and fewer cravings. Compared to a gastric bypass, a sleeve gastrectomy is an easier operation to perform.

Gastric bypass

In a gastric bypass operation, the stomach is divided into two parts. The smaller top part of the stomach is connected to the small intestine. The rest of the stomach, which is larger, is left in the body and continues to produce gastric juices, which are fed into the lower part of the small intestine. In this way, most of the stomach is bypassed. The newly formed stomach only has a volume of about 20 millilitres. 

Sleeve gastrectomy

In a sleeve gastrectomy, a crescent-shaped part of the stomach is separated and removed from the body. The remaining part is stitched back up. This gives the stomach a tubular shape. Unlike a gastric bypass, this procedure cannot be reversed. 

In the past, it was thought that the weight loss had two reasons. On the one hand, you eat less with a smaller stomach because you get full faster. On the other hand, the body doesn’t fully digest food. This is because parts of the stomach – and in the case of a gastric bypass, also parts of the duodenum and small intestine – are bypassed as a result of bariatric surgery, which means the body absorbs fewer calories. However, we now know that the main reason for the weight loss is that the hormonal balance changes: immediately after bariatric surgery, the patient is less hungry, has less appetite and also fewer cravings.

In order to at least partially achieve these hormonal changes, simply reducing the size of the stomach is sufficient. Bypassing parts of the digestive tract, as is the case with a gastric bypass, is not necessary for this. The sleeve gastrectomy procedure is therefore increasingly being performed in many countries. 

Those who decide to have bariatric surgery have to make long-term changes to their eating habits. If they don’t, they are at risk of experiencing digestive problems.

It is important to eat small portions only and to chew the food thoroughly. Foods high in sugar, meat with long fibres (e.g. thighs) and some vegetables should be avoided. Drinking during meals is no longer permitted. You must stop drinking 30 minutes before a meal, and should not drink anything again until at least 30 minutes after a meal. When you do have something to drink, it’s best to just take sips. The reason for this is that otherwise, the smaller stomach will fill up with liquid quite quickly when eating. This leaves little to no room for food. Additionally, in the case of a gastric bypass, chyme that isn’t fully digested can enter the small intestine too quickly. This so-called “dumping syndrome” can lead to digestive and circulation problems.

Because nutrient absorption is severely impaired as a result of bariatric surgery, patients also have to take dietary supplements for the rest of their lives, usually in the form of tablets, but some, like iron, are also administered through an infusion, or, like vitamin B12, through an injection.

Some risks are related to the operation itself. For example, there may be problems with the anaesthetic, or blood loss could occur during the procedure. However, because doctors now have a lot of experience with bariatric surgery, these risks are low.

Many people who have had bariatric surgery suffer from digestive problems. These include symptoms such as belching, vomiting and diarrhoea. Patients may also experience what’s known as greasy stool.

Since the body doesn’t fully digest food, malnutrition can also occur. To prevent this from happening, the procedure should be performed in a certified hospital that guarantees lifelong post-operative care.

No. In some cases, people may regain weight after they’ve lost it. This is possible even after a gastric bypass operation. Unfortunately, there are currently no definitive figures on how many people are affected by this in Switzerland.