Bariatric surgery, also referred to as weight loss surgery and metabolic surgery, and is treatment option for people with severe obesity. Bariatric surgery should be seen as part of a comprehensive approach, which includes lifestyle management.

How surgery works

Most weight loss surgeries are performed using minimally invasive techniques (laparoscopic surgery). The most common bariatric surgery procedures performed in the UK and worldwide are gastric bypass, and sleeve gastrectomy. Other less common procedures include adjustable gastric band, single-anastomosis gastric bypass and biliopancreatic diversion with duodenal switch.

Bariatric procedures were initially designed to cause weight loss by restricting the amount of food that can be eaten and/or causing malabsorption, which means that food passes through the gut without being absorbed properly. However, we now know that gastric bypass and sleeve gastrectomy work mainly by altering signals that come from the gut, which in turn control appetite, a person’s interest in food, taste and blood sugar. These changes in gut signals overcome/ trick the body’s fat defense mechanisms that normally make sustained weight loss difficult.

Bariatric surgery leads to changes in signals from the gut, including increasing appetite suppressing signals (peptide YY and glucagon-like peptide-1) and reducing appetite stimulating signals (ghrelin).

Weight management after surgery

Sustained weight loss after bariatric surgery is not guaranteed. The amount of weight that a person loses after surgery is variable with some people losing <10% of their initial body weight and other people losing too much weight. Post-surgery behavioural, nutritional and physical exercise changes are important and but research studies show that a person’s genes play a key role.  It is important to remember that obesity is a progressive condition and with time additional treatments are likely to be needed even in people who have undergone bariatric surgery.

Surgical options

There are various surgical options to choose from when considering bariatric surgery. If you are considering surgery you will need to discuss the risks and benefits of surgery with your surgical team.

Adjustable Gastric Banding

The Adjustable gastric band involves an inflatable band that is placed around the upper portion of the stomach, creating a small stomach pouch above the band, and the rest of the stomach below the band.

gastric band
Gastric Bypass

Gastric bypass has been performed as a treatment for severe obesity since 1960’s. The surgery involves stapling across the stomach to create a small pouch (size of an egg), the ‘new’ stomach. The rest of the stomach remains but food does not go into this. The small intestine is re-plumbed creating a short cut from the new stomach to the mid-part of the small intestine, bypassing the first part of the small intestine.

Gastric bypass works by several mechanisms. Most importantly, the rerouting of the food stream alters gut signals leading to increased satiety, reduced hunger, changes in taste and improved blood sugar. In addition, the newly created stomach pouch is considerably smaller and facilitates significantly smaller meals, which translates into less calories consumed.

On average people lose 20-30% of their total body weight. Gastric bypass requires adherence to dietary recommendations, lifelong vitamin/mineral supplementation, and follow-up compliance. The surgery can be reversed if required.

gastric bypass3
Sleeve Gastrectomy

Sleeve gastrectomy as a standalone procedure has only bee undertaken since 2008. The surgery involves removing 80% of the stomach, which is then removed. The rest of the gastrointestinal tracts remain untouched.

The surgery alters gut signals that regulate appetite, taste and blood sugar. The new stomach sleeve holds considerably smaller volume than the normal stomach and helps to significantly reduce the amount of food (and thus calories) that can be consumed. Short-term studies show that the sleeve is as effective as gastric bypass in terms of weight loss and improvement or remission of diabetes.

On average people lose 20-30% of their total body weight. Requires adherence to dietary recommendations, life-long vitamin/mineral supplementation, and follow-up compliance. The surgery is irreversible.

One Anastomosis Gastric Bypasss

One anastomosis gastric bypass is a relatively new operation first performed in 1997. This involves stapling the stomach starting from its lower part (known as the antrum) to create a long gastric pouch. The rest of the stomach remains but food does not go into this (hence the name bypass). The small intestine is then connected to the bottom of this pouch in such a way that the first part is bypassed. Few research studies have examined the changes after this operation but it is thought to work mainly through altering gut signals which control appetite, taste and blood sugar but also through restricting the size of the stomach. The re-plumbing means that bile contents can pass into the stomach and food pipe. At the moment it is unclear whether this might increase the risk of stomach cancer.

On average people lose 25-30% of their total body weight. One Anastomosis Gastric Bypass requires adherence to dietary recommendations, life-long vitamin/mineral supplementation, and follow-up compliance.

Mini Gastric Bypass new3
Bilio-Pancreatic Diversion With Duodenal Switch (BPD-DS)

The stomach is stapled and the outer 80% is removed. The intestines are re-plumbed so that food passes from the stomach into the distal part of the small intestine (further down than with a gastric bypass). The surgery works by altering gut signals that regulate appetite, taste and blood sugar. In addition, the stomach size is reduced and the absorption of fats and nutrients is reduced.

On average people lose 30-40% of their total body weight. This operation carries the greatest risk of nutritional deficiencies and the sleeve component is irreversible.

duodenal switch2

Bariatric surgery for people with type 2 diabetes

Blood sugar levels are usually markedly improved immediately following bariatric surgery before any weight loss occurs. This means that most people can reduce the number of medications or stop their medications. The term diabetes remission is used to describe people whose blood indicator of type 2 diabetes, HbA1c returns to the normal range without any medications for a year a more. Importantly, the long-term complications of type 2 diabetes such as kidney disease, neuropathy and eye problems are reduced by around a third following bariatric surgery. The chances of going into remission depend on how long a person has had type 2 diabetes for prior to surgery; the closer to diagnosis the greater the chances which is why NICE recommend an expedited referral for assessment for bariatric surgery for people with type 2 diabetes duration of 10 years or less. The likelihood of type 2 diabetes remission also depends on the severity of a person’s diabetes (current HbA1c and current medications) but even in the absence of remission bariatric surgery will lead to improved glucose control and reduce the number of medications needed for people with type 2 diabetes.