Bariatric surgery, also referred to as weight loss surgery and metabolic surgery, and is treatment option for people with severe obesity who fulfill NICE guidance criteria (see next section). Bariatric surgery is a term used to describe a group of procedures that are performed to facilitate weight loss. Importantly bariatric surgery should be seen as part of a comprehensive approach, which includes lifestyle management.
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, mini-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 many gut signals including increasing blood levels of the gut hormones peptide YY and glucagon-like peptide-1 (which reduce appetite) and reducing blood levels of ghrelin (which stimulates appetite), alterations in bile acids, the microbiome and nerve signals that come from the gut.
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.