Patient information from BMJ

Obesity - drugs and surgery

Last published:Mar 17, 2020

If you're obese, you weigh much more than is healthy for you. This is the result of regularly eating more calories than your body uses. The extra calories are stored as fat.

You can use our information to talk to your doctor and decide which treatments are best for you.

What is obesity?

Being obese means being very overweight. This can greatly increase your chance of serious health problems such as diabetes, high blood pressure, arthritis, heart disease, and some cancers.

Losing weight isn't easy. If changing your diet and exercising aren't helping you lose enough weight, your doctor might suggest you also take weight loss medicines. And if your weight is putting your health at high risk, your doctor might recommend having weight loss surgery.

When doctors talk about reaching a 'healthy' weight, they mean getting to a weight that lowers your risk of these health problems. It's not about how thin you would like to look.

Most doctors use the body mass index (BMI for short) to work out whether someone is at a healthy weight. Your BMI is a single number that's calculated based on your height and your weight.

Doctors say someone is obese if their BMI is 30 or higher. If someone has a BMI of 40 or higher, doctors say the person is extremely obese.

What treatments work?

To lose weight, you need to take in less energy, in the form of food and drinks, than you use. Many people do this through a weight loss programme that combines:

• eating a low-calorie diet. There are many diets you can follow. But research suggests that low-carbohydrate or low-glycaemic diets might work best.

• exercising regularly, and

• having behavioural therapy to help them change how they eat and exercise.

Some people also take medicines to help them lose weight. But they still need to follow a low-calorie diet and exercise regularly. These medicines can also have side effects.

If your weight is putting your health at high risk (for example, if you are extremely overweight or if you cannot breathe properly) you may need to lose weight quickly by having surgery. But this is often used as a last resort.

Medicines

There are currently only a few medicines that can be prescribed for weight loss. The most commonly prescribed one is called orlistat.

Orlistat doesn’t stop you feeling hungry, but it stops your body absorbing some of the fat from the food you eat. When you take orlistat about one third of the fat you eat passes straight out of your body in your stools.

Taking orlistat while following a low-calorie diet and exercising regularly can increase your chance of losing about 5 percent of your body weight over a year.

Most people taking orlistat get some side effects, which may discourage them from taking the medicine. These include:

• an oily leakage from their bowels

• diarrhoea that comes on very quickly

• frequent wind, and

• nausea and vomiting.

You may be able to avoid these side effects by making sure that your meals contain no more than 30 percent fat. That means that for every 100 grams of food you eat, not more than 30 grams of it should be fat. Talk to your doctor or a dietitian about how to do this.

Orlistat can stop you from absorbing vitamin D, vitamin E, vitamin K, and beta-carotene (vitamin A). Your doctor may recommend vitamin supplements.

Liraglutide is a medicine that is usually used to treat diabetes. But it is sometimes prescribed to help people to lose weight. Side effects can include dizziness and an upset stomach

You might have heard of a weight-loss medicine called lorcaserin. This is not used in many countries, including the UK, the US, and the European Union, because it is not considered safe. Lorcaserin has been linked to increased cancer risk.

If you have been prescribed lorcaserin, you should talk to your doctor about other treatments instead.

Weight loss (bariatric) surgery

If you're extremely obese, surgery to make your stomach smaller can help you eat less and lose weight. This is called weight loss surgery, or bariatric surgery.

Weight loss surgery is a major operation. Your doctor will need to make sure you meet certain requirements before considering surgery.

Surgery is usually done only if your weight is dangerous to your health, and if you've tried other ways of losing weight. You need to follow a strict diet after the operation.

There are several types of weight loss surgery. The main ones are:

• gastric bypass: The surgeon staples a small pouch in the top of your stomach. Your small bowel is cut away from the lower part of your stomach, shortened, and reattached to the pouch. The rest of your stomach is closed off

• gastric banding: An adjustable band makes a small pouch in the top part of your stomach

• biliopancreatic diversion: The bottom part of your stomach is removed so your stomach is smaller. Your small bowel is shortened and reattached to the stomach

• sleeve gastrectomy: This operation closes off three-quarters of the stomach, leaving a narrow tube.

People can lose a lot of weight after weight loss surgery, with some losing between 40 percent and 100 percent of their excess body weight. People with type 2 diabetes or high blood pressure sometimes find that these conditions greatly improve after they've had surgery.

The amount of weight you lose depends on what you eat and how much exercise you do after surgery. Surgery doesn't work for everyone. Some people don't lose any weight, or put most of it back on.

You will have to change how you eat after surgery, as you will only be able to eat a small amount before your stomach is full. Some people have problems with their digestion, including nausea, diarrhoea, constipation, indigestion, and heartburn. You may also need to take supplements to make sure you get all the vitamins you need.

Some people get problems from surgery, such as infections, bleeding, and pneumonia. Being treated by an experienced surgeon, and in a hospital where surgeons do lots of operations for obesity, reduces the chance of problems.

There's a small chance that you will die during surgery or shortly afterwards. About three in every 1000 people die during surgery or in the following month.

To reduce your chance of problems during and after surgery, you may need to lose some weight before your operation. It's also best to give up smoking before surgery.

What will happen to me?

If you're obese, the benefits of losing weight are many. You will feel better and have a much lower chance of serious health problems, including heart disease, cancer, diabetes, and arthritis. Losing weight can be difficult, but medicines or surgery can help some people.