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07 September 2011

Rare surgery for weight loss

A less common form of obesity surgery may spur more weight loss than its far more popular cousin, gastric bypass – but at the price of greater long-term risks.

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A less common form of obesity surgery may spur more weight loss than its far more popular cousin, gastric bypass – but at the price of greater long-term risks, researchers reported.

The study, published in the Annals of Internal Medicine, followed 60 severely obese patients who were randomly assigned to either gastric bypass surgery or a more extensive procedure known as duodenal switch.

Two years after surgery, duodenal switch patients had lost more weight: about 23 kilos more, on average.

People shed a substantial amount of weight with either type of surgery. Gastric bypass patients cut an average of 50 kilos, while duodenal switch patients dropped about 74. But those extra kilos came with nearly double the complication rate.

Of the 29 duodenal switch patients, 62% had problems like abdominal pain, vomiting, diarrhoea and intestinal obstruction. And several suffered long-term malnutrition – something not seen in the gastric bypass group.

Duodenal switch is not a popular procedure. In a 2008 study, it accounted for just 1% of weight-loss, or bariatric, surgeries done in the US, and 5% in Europe.

Not for everyone

The technique is often reserved for "super obese" patients with a body mass index (BMI) of 50 or higher – though some surgeons perform it with less severely obese patients too, explained Dr Torgeir T. Sovik of Oslo University in Norway, the lead researcher on the new study.

"As duodenal switch can be associated with more adverse events, this procedure should only be performed in carefully selected patients by a dedicated bariatric team," he said. "And a closer follow-up after surgery is required after such procedures." But an expert not involved in the study went further.

"This is an operation that should probably go away," said Dr. Edward H. Livingston, a professor and surgeon at the University of Texas Southwestern Medical Center in Dallas.

The average weight loss seen with either gastric bypass or duodenal switch will improve or reverse obesity-related ills like diabetes, sleep apnoea and knee arthritis, according to Livingston, who wrote an editorial published with the study.

So for those medical conditions, it probably wouldn't matter if a person lost 45 kilos or 68 kilos over two years. BMI is a measure of weight relative to height. A BMI between 18.5 and 24.9 is considered normal weight, and above 30 is obese. The patients in the current study were a fairly healthy group, despite having a BMI of 50 or more.

Some cholesterol improvement

After two years, those who'd had a duodenal switch showed a greater improvement in their cholesterol levels. But those levels were near-normal (in both groups) to begin with, Livingston noted.

That begs the question, he said, of whether the extra weight loss "actually accomplished anything".

"The answer is no," Livingston said. In the US, where about 220,000 people underwent weight-loss surgery in 2009, gastric bypass is the most common form chosen.

During gastric bypass, the upper portion of the stomach is stapled off to create a smaller pouch that restricts the amount of food a person can eat at one time. The surgeon also creates a bypass around the rest of the stomach and a portion of the small intestine, which limits the body's absorption of food.


Duodenal switch is more extensive. The surgeon removes part of the stomach, and the remaining "sleeve"-like stomach is attached to the final section of the small intestine, that puts even greater limits on the body's absorption of kilo joules and nutrients.

Both surgeries carry the long-term risk of nutritional deficiencies, and people need to take supplements and carefully monitor their diets for a lifetime afterward.

Nutrient deficiencies

But the risks of nutrient deficiencies are greater with duodenal switch, and include some not seen with gastric bypass, Livingston pointed out.

Some people, for instance, may have severe calcium and vitamin D loss, leading to weak and fragile bones. Other problems include severe protein deficiency and night blindness caused by vitamin A deficiency (which is also reversible with extra vitamin A treatment).

In this study, three of the 29 duodenal switch patients developed protein malnutrition, two developed night blindness, and one had a severe iron deficiency that needed to be treated with iron infusions.

Livingston said his advice to people considering weight-loss surgery is to avoid duodenal switch. "It's just not a good operation," he asserted.

But he also questioned the value of weight-loss surgery, in general, for severely obese people who do not have medical conditions that stand to improve or resolve after surgery. 

Caution in order

In general, experts say that surgery could be an option for anyone with a BMI of 40 or higher; that translates, roughly, to a man who is at least 45 kilos overweight or a woman who is 36 kilos overweight.

Livingston said he thinks more caution is in order when a very obese person is otherwise healthy.

Along with the risks of surgery, he said, there is still uncertainty about whether it actually lengthens people's lives. Some studies have suggested it might, but not all.

In a study recently published in the Journal of the American Medical Association, Livingston and his colleagues found no survival advantage among severely obese patients who had undergone weight-loss surgery versus those who hadn't.

The study involved 850 US veterans who underwent some form of weight-loss surgery, at an average age of about 50, and more than 41,000 vets who had only non-surgical care. There was no evidence that surgery improved longevity over the next seven years.

"We really don't even know if there's a survival benefit," Livingston said. That, he added, makes the risks of duodenal switch seem even less worthwhile. But according to Sovik, duodenal switch might be appropriate for some super obese patients.

Longer-term studies needed

In the US, he said, about one in three weight-loss surgery candidates have a BMI of 50 or higher. And studies suggest that a sizable percentage of those people will still have a BMI higher than 40 after gastric bypass.

In this study, one-quarter of gastric bypass patients still had a BMI that high two years after surgery – versus none of the duodenal switch patients. More extensive monitoring after duodenal switch, Sovik noted, can help detect and manage side effects.

He pointed out, though, that larger, longer-term studies are still needed to show whether the extra weight loss with duodenal switch ultimately improves severely obese patients' health and extends their lives.

(Reuters Health, Amy Norton, September 2011) 

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