News / Health

After Weight-loss Surgery, New Gut Bacteria Keep Obesity Away

FILE - An overweight woman sits on a chair in Times Square in New York, May 8, 2012.
FILE - An overweight woman sits on a chair in Times Square in New York, May 8, 2012.
Reuters
— The logic behind weight-loss surgery seems simple: rearrange the digestive tract so the stomach can hold less food and the food bypasses part of the small intestine, allowing fewer of a meal's calories to be absorbed.

Bye-bye, obesity.

A study of lab mice, published on Wednesday, begs to differ.

It concludes that one of the most common and effective forms of bariatric surgery, called Roux-en-Y gastric bypass, melts away pounds not - or not only - by re-routing the digestive tract, as long thought, but by changing the bacteria in the gut.

Or, in non-scientific terms, the surgery somehow replaces fattening microbes with slimming ones.

If that occurs in people, too, then the same bacteria-changing legerdemain achieved by gastric bypass might be accomplished without putting obese patients under the knife in an expensive and risky operation.

"These elegant experiments show that you can mimic the action of surgery with something less invasive," said Dr. Francesco Rubino of Catholic University in Rome and a pioneer in gastric-bypass surgery. "For instance, you might transfer bacteria or even manipulate the diet to encourage slimming bacteria and squelch fattening kinds," said Rubino, who was not involved in the study.

Fattening Bugs, Slimming Bugs

For many obese patients, particularly those with type 2 diabetes, gastric bypass has succeeded where nothing else has. Severely obese patients routinely lose 65 to 75 percent of their excess weight and fat after the operation, studies show, and leave their diabetes behind.

Oddly, however, the diabetes remission often occurs before significant weight loss. That has made bypass surgeons and weight-loss experts suspect that Roux-en-Y changes not only anatomy but also metabolism or the endocrine system. In other words, the surgery does something besides re-plumb the gut.

That "something," according to previous studies, includes altering the mix of trillions of microbes in the digestive tract. Not only are the "gut microbiota" different in lean people and obese people, but the mix of microbes changes after an obese patient undergoes gastric bypass and becomes more like the microbiota in lean people.

Researchers did not know, however, whether the microbial change was the cause or the effect of post-bypass weight loss.

That is what the new study, by researchers at Massachusetts General Hospital and Harvard University, set out to answer.

They first performed Roux-en-Y on obese mice. As expected, the animals quickly slimmed down, losing 29 percent of their weight and keeping it off, the researchers report in the journal Science Translational Medicine.

To make sure there was not something about the general experience of surgery, rather than gastric bypass specifically, that affected the animals, the scientists performed "sham" Roux-en-Y on other obese mice. In this procedure, the researchers made incisions as if they were going to do a gastric bypass, but instead connected everything up as nature had it.

The researchers then transferred gut microbiota from the Roux-en-Y mice to microbe-free obese mice. Result: the recipient mice lost weight and fat - no surgery required. Crucially, obese mice that received gut bugs from mice that had received sham Roux-en-Y, not the real thing, did not slim down.

It is the first experimental evidence that changes in the gut microbiota cause the weight loss after gastric bypass, and that the new, post-bypass mix of microbes can cause weight loss in animals that did not have surgery.

In particular, just a week after surgery the Roux-en-Y mice harbored relatively more of the same types of bacteria that become more abundant in people after gastric bypass and that lean people have naturally.

"The effects of gastric bypass are not just anatomical, as we thought," said Dr. Lee Kaplan, senior author of the study and associate professor of medicine at Harvard Medical School. "They're also physiological. Now we need to learn more about how the microbiota exert their effects."

Slimming bacteria work their magic in either of two ways, studies of gut microbiota show. They seem to raise metabolism, allowing people to burn off a 630-calorie chocolate chip muffin more easily.

They also extract fewer calories from the muffin in the first place. In contrast, fattening bacteria wrest every last calorie from food.

Transferring slimming bacteria into obese people might be one way to give them the benefits of weight-loss surgery without an operation. It might also be possible to devise a menu that encourages the proliferation of slimming bacteria and reduces the population of fattening bacteria.

Another new study found that figuring out whether you have slimming microbiota or fattening ones might be as easy as breathing.

In a study published on Tuesday in the online edition of the Journal of Clinical Endocrinology & Metabolism, researchers at Cedars-Sinai Medical Center in Los Angeles report that people whose breath has high concentrations of both hydrogen and methane gases are more likely to have a higher body mass index and higher percentage of body fat.

Methane is associated with bacteria called Methanobrevibacter smithii, which in overabundance may cause weight gain by extracting calories from food super-efficiently, Cedars' Ruchi Mathur, who led the study, said: "It could allow a person to harvest more calories from their food."

The breath test could provide a warning that someone is at risk of obesity because he harbors fattening microbiota.

It could also validate what many overweight people have long suspected: if their slim friends eat two slices of bacon-cheeseburger pizza the 600 calories go through them like celery, but if the overweight person indulges then every calorie seems to turn into more fat. People absorb different quantities of calories from the exact same food, thanks to their gut microbiota.

You May Like

Lebanese Media Unite to Support Palestinians in Gaza

Joint newscast billed as Arab world’s first unified news bulletin in support of Hamas-controlled Gaza Strip More

Photogallery Australian PM Alleges ‘Coverup’ at MH17 Crash Site

Meanwhile, Russia's ambassador to Malaysia denies plane's black boxes were opened before they were handed over to Malaysian officials More

Despite Advances in AIDS Treatment, Stigma Lingers

Leading immunologist tells VOA that stigma is often what prevents those infected with disease from seeking treatment More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
IAEA: Iran Turns its Enriched Uranium Into Less Harmful Formi
X
July 22, 2014 10:26 AM
Iran has converted its stockpiles of enriched uranium into a less dangerous form that is more difficult to use for nuclear weapons, according to the United Nations’ Atomic Energy Agency. The move complies with an interim deal reached with Western powers on Iran's nuclear program last year, in exchange for easing of sanctions. Henry Ridgwell reports for VOA from London.
Video

Video IAEA: Iran Turns its Enriched Uranium Into Less Harmful Form

Iran has converted its stockpiles of enriched uranium into a less dangerous form that is more difficult to use for nuclear weapons, according to the United Nations’ Atomic Energy Agency. The move complies with an interim deal reached with Western powers on Iran's nuclear program last year, in exchange for easing of sanctions. Henry Ridgwell reports for VOA from London.
Video

Video Relic of Saint Draws Catholics Worried About Immigration Issue

A Roman Catholic saint who is a figure of devotion for those crossing the border into the United States is attracting believers concerned about the plight of undocumented immigrants. Mike O'Sullivan reports from Los Angeles, where a relic of Saint Toribio has drawn thousands to local churches.
Video

Video Ukraine Rebels Surrender MH17 Black Boxes

After days of negotiations, a senior separatist leader handed over two black boxes from an airliner downed over eastern Ukraine to Malaysian experts early Tuesday. While on Monday, the U.N. Security Council unanimously demanded that armed groups controlling the crash site allow safe and unrestricted access to the wreckage.
Video

Video In Cambodia, HIV Diagnosis Brings Deadly Shame

Although HIV/AIDS is now a treatable condition, a positive diagnosis is still a life altering experience. In Cambodia, people living with HIV are often disowned by friends, family and the community. This humiliation can be unbearable. We bring you one Cambodian woman’s struggle to overcome a life tragedy and her own HIV positive diagnosis.
Video

Video Nature of Space Exploration Enters New Age

Forty-five years ago this month, the first humans walked on the moon. It was during an era of the space race between the United States and the Soviet Union. World politics have changed since then and -- as Elizabeth Lee reports -- so has the nature of space exploration.
Video

Video Chicago’s Argonne Lab Developing Battery of the Future

In 2012, the U.S. Department of Energy’s Office of Science awarded a $120 million grant to a new technology center focused on battery development - headquartered at Argonne National Laboratory in suburban Chicago, Illinois. As VOA’s Kane Farabaugh reports, there scientists are making the next technological breakthroughs in energy storage.
Video

Video In NW Pakistan, Army Offensive Causes Massive Number of Displaced

Pakistan’s army offensive in North Waziristan has resulted in the large-scale displacement of the local population. VOA's Ayaz Gul reports from northwest Pakistan where authorities say around 80 percent of the estimated 1 million internally displaced persons [IDPs] have settled in Bannu district, while much of the remaining 20 percent are scattered in nearby cities.
Video

Video Kurdish Peshmerga Force Secures Kirkuk, Its Oil

The Kurdistan regional government has sent its Peshmerga troops into the adjacent province of Kirkuk to drive out insurgents, and to secure the area's rich oil fields. By doing this, the regional government has added a fourth province to the three it officially controls. The oil also provides revenue that could make an independent Kurdistan economically strong. VOA’s Jeffrey Young went out with the Peshmerga and filed this report.
Video

Video Malaysia Reeling: Second Air Disaster in Four Months

Malaysia is reeling from the second air disaster in four months involving the country’s flag carrier. Flight 340 vanished in March and despite an extensive search, no debris has been found. And on Thursday, Flight 17, likely hit by a surface-to-air missile, came apart over eastern Ukraine. The two incidents together have left more than 500 people dead. VOA Correspondent Steve Herman reports from Kuala Lumpur.

AppleAndroid