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

Hostage Crisis Could Divide Japan Over Plans to Boost Military

Japanese Chief Cabinet Secretary Yoshihide Suga said Monday the government is working closely with the Jordanian government to secure the release of remaining Japanese hostage Kenji Goto More

Video Brussels Shaken as New Greek Leader Challenges Europe’s Austerity Drive

Country's youngest ever PM Alexis Tsipras, 40, sworn in Monday and says he will restore dignity to Greece by ending spending cuts More

Multimedia National Geographic Photo Camps Empower Youth

Annual mentoring program's mission is to give young people a voice to tell their own stories through photography More

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Obama Urges Closer Economic Ties During Historic India Visiti
X
Aru Pande
January 26, 2015 9:33 PM
U.S. President Barack Obama says the United States and India must do better to capitalize on untapped potential in their economic relationship - by removing some of the roadblocks to greater trade and investment. As VOA correspondent Aru Pande reports from New Delhi, Obama spoke after participating in India’s Republic Day celebration.
Video

Video Obama Urges Closer Economic Ties During Historic India Visit

U.S. President Barack Obama says the United States and India must do better to capitalize on untapped potential in their economic relationship - by removing some of the roadblocks to greater trade and investment. As VOA correspondent Aru Pande reports from New Delhi, Obama spoke after participating in India’s Republic Day celebration.
Video

Video US, EU Threaten New Russia Sanctions Over Ukraine

U.S. President Barack Obama has blamed Russia for an attack by Ukrainian separatists that left dozens dead in the port of Mariupol and cast further doubt on the viability of last year’s cease-fire with the Kyiv government. VOA’s Michael Bowman reports from Washington.
Video

Video White House Grapples With Yemen Counterterrorism Strategy

Reports say the U.S. has carried out a drone strike on suspected militants in Yemen, the first after President Barack Obama offered reassurances the U.S. is continuing its counterterrorism operations in the country. The future of those operations has been in question following the collapse last week of Yemen’s government. VOA White House correspondent Luis Ramirez reports.
Video

Video Kerry Warns Against Violence in Nigeria Election

US Secretary of State John Kerry visited Nigeria Sunday in a show of the level of concern within the U.S. and the international community over next month’s presidential election. Chris Stein reports.
Video

Video Zoo Animals Show Their Artistic Sides

The pursuit of happiness is so important, America's founding fathers put it in the Declaration of Independence. Any zookeeper will tell you animals need enrichment, just like humans do. So painting, and even music, are part of the Smithsonian National Zoo's program to keep the animals happy. VOA’s June Soh met some animal artists at the zoo in Washington. Faith Lapidus narrates.
Video

Video Worldwide Photo Workshops Empower Youth

Last September, 20 young adults from South Sudan took part in a National Geographic Photo Camp. They are among hundreds of students from around the world who have learned how to use a camera to tell the stories of the people in their communities through the powerful medium of photography. Three camp participants talked about their experiences recently on a visit to Washington. VOA’s Julie Taboh reports.
Video

Video Saudi, Yemen Developments Are Sudden Complications for Obama

The death of Saudi Arabia's King Abdullah and the collapse of Yemen’s government have cast further uncertainty on U.S. efforts to fight militants in the Middle East and also contain Iran’s influence in the region. VOA White House correspondent Luis Ramirez reports on the new complications facing the Obama administration and its Middle East policy.
Video

Video Progress, Some Areas of Disagreement in Cuba Talks

U.S. and Cuban officials are reporting progress from initial talks in Havana on re-establishing diplomatic ties. U.S. Assistant Secretary of State (for Western Hemisphere Affairs) Roberta Jacobson said while there was agreement on a broad range of issues, there also are some “profound disagreements” between Washington and Havana. VOA State Department correspondent Pam Dockins has the story.
Video

Video US, Japan Offer Lessons as Eurozone Launches Huge Stimulus

The Euro currency has fallen sharply after the European Central Bank announced a bigger-than-expected $67 billion-a-month quantitative easing program Thursday - commonly seen as a form of printing new money. Henry Ridgwell reports for VOA from London on whether the move might rescue the eurozone economy -- and what lessons have been learned from similar programs around the world.
Video

Video Nigerian Elections Pose Concern of Potential Conflict in 'Middle Belt'

Nigeria’s north-central state of Kaduna has long been the site of fighting between Muslims and Christians as well as between people of different ethnic groups. As the February elections approach, community and religious leaders are making plans they hope will keep the streets calm after results are announced. Chris Stein reports from the state capital, Kaduna.
Video

Video As Viewership Drops, Obama Puts His Message on YouTube

Ratings reports show President Obama’s State of the Union address this week drew the lowest number of viewers for this annual speech in 15 years. White House officials anticipated this, and the president has decided to take a non-traditional approach to getting his message out. VOA White House correspondent Luis Ramirez reports.
Video

Video S. Korean Businesses Want to End Trade Restrictions With North

Business leaders in South Korea are calling for President Park Geun-hye to ease trade restrictions with North Korea that were put in place in 2010 after the sinking of a South Korean warship.Pro-business groups argue that expanding trade and investment is not only good for business, it is also good for long-term regional peace and security. VOA’s Brian Padden reports.

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

All About America

AppleAndroid