If you have severe obesity and haven't been able to lose weight, your doctor may recommend weight-loss surgery. Weight-loss surgery (bariatric surgery) may help you lose weight. Losing weight can lower your risk for weight-related problems, such as heart disease, diabetes, sleep apnea, high blood pressure, and arthritis.

Some bariatric surgeries are called restrictive surgeries because they limit how much food you can eat by limiting how much food can enter your stomach. One example is sleeve gastrectomy. Another type of bariatric surgery is called controlled malabsorption. This surgery makes it impossible for your body to break down and absorb food in a normal way. If your doctor recommends this type of surgery, you may have a surgery called biliopancreatic diversion with a duodenal switch (BPD-DS). Other bariatric surgeries combine both a restrictive with a malabsorptive part. This might be gastric bypass surgery.

BPD-DS is a complicated type of bariatric surgery. It changes the anatomy of your digestive system in several ways:

• It removes most of your stomach.
• It bypasses most of your small intestine. Food you eat won't flow through the bypassed part of the intestine.
• It sends digestive enzymes from your pancreas to an area much farther down in your small intestine.

These changes mean that your body does not have the time or the space to break down the fats, proteins, and carbohydrates from foods you eat into smaller particles that your body can absorb. This causes you to lose weight quickly. You are also likely to keep the weight off longer than with restrictive weight-loss surgeries. But you may also have more long-term complications.

After BPD-DS, you will be at high risk for many nutritional problems (deficiencies). The surgery makes it harder for you to digest and absorb fat. This can mean your body doesn't get enough of vitamins. A, D, E, and K. These vitamins are fat-soluble. This means they dissolve in fat when they are inside your body. If you can't absorb fat, you won't be able to fully absorb or store these vitamins.

You need vitamin D to help absorb calcium, so you can have too little calcium in your body after BPD-DS. This is a very real concern, especially for females. Females are more likely to have weak bones (osteoporosis).

Problems with absorbing fats may cause:

• Steatorrhea. Undigested fats cause loose and frequent bowel movements. These are often hard to control. You may have cramping, foul-smelling diarrhea, and lots of gas.
• Vitamin deficiencies and related diseases. Symptoms of these vitamin deficiencies include rashes, bruising or bleeding, night blindness, and weak bones that are more likely to break.
• Calcium deficiency. BPD-DS makes it harder for your body to absorb calcium and vitamin D. Both of these nutrients are important for healthy bones. Low levels of calcium in your body can cause broken bones.
• Vitamin E deficiency. This problem is rare, but it can happen with fat malabsorption. Symptoms include numbness or tingling in your arms and legs. This is because your nerves aren't working as they should. Other symptoms include muscle weakness and vision problems. You are also less able to fight off infections.

After BPD-DS, you will need to follow a diet high in protein. You will need to take high doses of fat-soluble vitamins every day. You may also need other dietary supplements. Limiting the amount of fat in your diet will help prevent steatorrhea. Some people may also need to take pancreatic enzyme supplements.

The American Society for Metabolic and Bariatric Surgery recommends that you start taking vitamin A, D, and K supplements about 2 to 4 weeks after BPD-DS surgery. This will help prevent nutritional deficiencies. You may also need calcium, iron, B-complex, and multivitamins. Talk with your doctor to find out what supplements you should take.

You'll need to take these supplements for the rest of your life. You will also need to be tested regularly by your doctor to check your nutrition and vitamin levels to prevent complications. Your doctor may need to change these guidelines to fit your particular condition as guided by your lab results.

Remember that fat malabsorption is the reason you lose weight after the surgery. But it could cause long-term complications. These risks can be managed, but they will last for the rest of your life. You will need a regular, lifelong follow-up schedule with a doctor. Contact your doctor if any symptoms after surgery get worse or you develop new symptoms. A quick follow-up will allow problems to be quickly addressed. Work with your doctor to look at all of the risks and benefits of BPD-DS as you get ready for bariatric surgery.