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Fat Malabsorption After Weight-Loss Surgery

If you are severely obese and have tried to lose weight without success, your doctor may recommend weight-loss surgery. Weight-loss surgery, or bariatric surgery, has been shown to be an effective way to lose weight and reduce the risk for weight-related problems such as heart disease, diabetes, sleep apnea, and arthritis.

Most bariatric surgeries are called restrictive surgeries because they restrict how much you can eat. Another type of bariatric surgery is called controlled malabsorption, which is designed to make it impossible for the body to break down and absorb food in a normal way. If your doctor recommends this type of surgery, a commonly performed procedure is duodenal switch with biliopancreatic diversion (BPD-DS).

About BPD-DS and malabsorption

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

  • It removes about 70 percent of your stomach.

  • It bypasses most of your small intestine (ingested food does not flow through the bypassed part).

  • It reroutes 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 a rapid amount of weight loss that tends to last longer than restrictive type weight-loss surgeries but may also cause more long-term complications.

Fat malabsorption

After BPD-DS you will be at high risk for many nutritional deficiencies. Because fats are now the most difficult of foods to digest, fat malabsorption is a frequent problem. This, in turn, causes a problem with the absorption of certain vitamins. Vitamins A, D, E, and K are fat-soluble which means they dissolve in fat when they are inside your body. If you cannot absorb fat, you will not be able to fully absorb or store these vitamins.

You need vitamin D to help absorb calcium, so you can also run into problems with low calcium after BPD-DS. This is a very real concern, especially for women who have a higher rate of osteoporosis (weak bones). Studies show that four years after BPD-DS, about two-thirds of people will be low in vitamins A, D, and K, and half will be low in calcium.

Fat malabsorption may cause:

  • Steatorrhea. Undigested fats cause loose and frequent bowel movements that are often hard to control and are foul smelling and accompanied by lots of gas.

  • Vitamin deficiencies and related diseases. Symptoms of fat-soluble vitamin deficiencies include rashes, bruising or bleeding, night blindness, and weak bones prone to fracture.

  • Calcium deficiency.  Low levels of body calcium because of vitamin D deficiency can cause bone fractures.

  • Vitamin E deficiency. This is rare but can occur with fat malabsorption. Symptoms include poor nerve function that causes numbness or tingling, muscle weakness, poor vision, and decreased ability to fight infections.

Managing fat malabsorption after BPD-DS

After BPD-DS you will need to stay on a diet high in protein, and take vitamins every day. In addition to taking high doses of fat-soluble vitamins, you may also need vitamin B, iron, and calcium supplements. Limiting the fat content of your diet will help prevent steatorrhea. You may also need to take pancreatic enzyme supplements.

The American Society for Metabolic and Bariatric Surgery (ASMBS) recommends that you take these fat-soluble vitamin supplements every day, usually starting two to four weeks after BPD-DS surgery, to help prevent nutritional deficiencies:

  • 10,000 IUs of vitamin A

  • 2,000 IUs of vitamin D

  • 300 mcg of vitamin K

ASMBS also recommends that you have up to three servings of calcium-rich dairy beverages and take these additional supplements every day, starting the first day after discharge from the hospital, to prevent other nutritional shortfalls:

  • Multivitamin with 200 percent of the recommended daily values

  • Minimum of 18 to 27 mg of iron, and up to 50 to 100 mg a day for menstruating women or people at risk of anemia

  • 1,800 to 2,400 mg of calcium, in doses of 500 to 600 mg (don't combine them with supplements that contain iron—wait a couple of hours)

  • B-complex (optional)

You'll need to take these supplements for the rest of your life and be tested regularly by your doctor to prevent complications. Your doctor may need to adapt these guidelines to suit your individual condition.

Remember that fat malabsorption is both the reason for the weight loss following surgery and the cause of long-term complications. These risks can be managed, but they will last for the rest of your life. You will need to develop a regular lifelong follow-up schedule with a doctor. Work with your doctor to assess all the risks and benefits of BPD-DS as part of your preparation for bariatric surgery.