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

Republican Majority in Congress Off to Rough Start

Standoff over Homeland Security funding exposes philosophical, tactical problems within party More

Pakistan Blocks Baloch Activist from US Trip

Human Rights Commission of Pakistan slams Islamabad officials for stopping people from leaving country to attend human rights conference More

Video Muslims Long Thrived in North Carolina Before Students Killed

Idyll shattered February 10, when three Muslim university students living in Chapel Hill were gunned down by a neighbor More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Muslims Long Thrived in N Carolina Before Slaying of 3 Studentsi
X
Jerome Socolovsky
March 05, 2015 9:04 PM
The killings of three Muslim students in North Carolina early last month came as Muslims across the United States have felt under siege, partly as a result of terrorist attacks being committed internationally in the name of their faith. But Muslims have long thrived in university cities in this part of the American South. VOA's Jerome Socolovsky reports.
Video

Video Muslims Long Thrived in N Carolina Before Slaying of 3 Students

The killings of three Muslim students in North Carolina early last month came as Muslims across the United States have felt under siege, partly as a result of terrorist attacks being committed internationally in the name of their faith. But Muslims have long thrived in university cities in this part of the American South. VOA's Jerome Socolovsky reports.
Video

Video Fuel Shortages in Nigeria Threaten Election Campaigns

Nigeria is suffering a gas shortage as the falling oil price has affected the country’s ability to import and distribute refined fuels. Coming just weeks before scheduled March 28 elections, the shortage could have a big impact on the campaign, as Henry Ridgwell reports for VOA.
Video

Video Report: Human Rights in Annexed Crimea Deteriorating

A new report by Freedom House and the Atlantic Council of the United States says the human rights situation in Crimea has deteriorated since the peninsula was annexed by Russia in March of last year. The report says the new authorities in Crimea are discriminating against minorities, suppressing freedom of expression, and forcing residents to assume Russian citizenship or leave. Zlatica Hoke has more.
Video

Video 50 Years Later African-Americans See New Voting Rights Battles Ahead

Thousands of people will gather to mark the 50th anniversary of a historic civil rights march on March 7th in Selma, Alabama. In 1965, dozens of people were seriously injured during the event known as “Bloody Sunday,” after police attacked African-American demonstrators demanding voting rights. VOA’s Chris Simkins introduces us to some civil rights pioneers who are still fighting for voting rights in Alabama more than 50 years later.
Video

Video Craft Brewers Taking Hold in US Beer Market

Since the 1950’s, the U.S. beer industry has been dominated by a handful of huge breweries. But in recent years, the rapid rise of small craft breweries has changed the American market and, arguably, the way people drink beer. VOA’s Jeff Custer reports.
Video

Video Video Claims to Show Shia Forces in Iraq Executing Sunni Boy

A graphic mobile phone video is spreading on the Internet, claiming to show Iraqi forces or Shia militia executing a handcuffed Sunni boy. Experts have yet to verify the video, but already Islamic State followers are publicizing it across social media, playing on deep-rooted sectarian fears. VOA’s Jeff Seldin reports.
Video

Video Ukrainian Authorities Struggle to Secure a Divided Mariupol

Since last month's cease-fire went into effect, shelling around the port city of Mariupol has decreased, but it is thought pro-Russian separatists remain poised to attack. For the city’s authorities, a major challenge is gaining the trust of residents, while at the same time rooting out informants who are passing sensitive information to the rebels. Patrick Wells reports for VOA.
Video

Video Volunteer Gauge-Watchers Help Fine-Tune Weather Science

An observation system called CoCoRaHS is working to improve weather science, thanks to thousands of volunteers across the country who measure precipitation in their own backyards, then share their data through the Internet. VOA's Shelley Schlender reports.
Video

Video NASA Spacecraft Approaches a Dwarf Planet

NASA’s Dawn spacecraft will make history on Friday, March 6, when it becomes the first man-made object to orbit a dwarf planet named Ceres. It is located in the asteroid belt between Mars and Jupiter, almost 500 million kilometers from Earth. Among other objectives, Dawn will try to examine two mysterious bright white spots detected on the planet’s surface. VOA’s George Putic has more.
Video

Video Young Muslims Radicalized Online

Young Muslims are being radicalized ‘in their bedrooms’ through direct contact with Islamic State or ISIL fighters via the Internet, according to terror experts. There are growing concerns that authorities and Internet providers are not doing enough to counter online extremism - which analysts say is spread by a prolific network of online supporters around the world. Henry Ridgwell reports from London.
Video

Video Positive Messaging Transforms Ethiopia's Image

Ethiopia was once known for famine and droughts. Now, headlines more often point to its fast-growing economy and its emergence as a regional peacemaker. How has Addis Ababa changed the narrative? VOA's Marthe van der Wolf reports.
Video

Video Answers Elude Families of MH370 Passengers

For the families on board Malaysia Airlines flight MH370, an airline official’s statement nearly one year ago that the plane had lost contact with air traffic control at 2:40 AM is the only thing that remains confirmed. William Ide reports.

All About America

Circumventing Censorship

An Internet Primer for Healthy Web Habits

As surveillance and censoring technologies advance, so, too, do new tools for your computer or mobile device that help protect your privacy and break through Internet censorship.
More