How eating microbes may aid in weight loss

If you could lose weight by consuming special bacteria, would you do it? It sounds weird, but some scientists have hope that a new microbial treatment could one day help control the obesity epidemic.

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The new science

At a meeting of the American Chemical Society in March, researchers presented results from a study on mice given a high-fat diet. Half of the mice were also given water containing microbes engineered by the researchers.

“We engineered our bacteria to make a satiety factor, NAPE, that is normally made by the intestinal tract,” says lead researcher Sean Davies, an assistant professor at Vanderbilt University School of Medicine. A satiety factor is a molecule that tells the brain you’re full— so basically, Davies and his team created an appetite-suppressing bacteria.

“In obese people, it appears that the intestinal tract fails to make enough NAPE in response to a meal, so there is a weaker signal to the brain that enough food has been eaten,” Davies says. The NAPE-producing bacteria could act as a satiety supplement, then. In the study, the mice who drank the NAPE water gained 15 percent less weight over 12 weeks.

Microbial support

This isn’t the first time microbes have been researched for weight-regulating properties. In recent years, medical researchers have begun wondering just how important gut bacteria are to overall health.

“A lot of scientists are working very hard to try to answer that question right now,” Davies says. “The gut microbiota of individuals with various chronic diseases often differs substantially from that of healthy individuals,” he says, “but in many cases we still need to understand if that is a cause or an effect of the disease.”

Of course, high on the list of research priorities is obesity, which is blamed for many chronic diseases. In 2013, researchers from Cedars-Sinai School of Medicine wanted to find out if a particular sort of microorganism, methane-producing microbes called methanogens, were linked to obesity. 

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The researchers measured the levels of methane and hydrogen in the breath of 792 people and found that heavier people indeed had higher levels. The researchers think that overpopulation of a certain methane- and hydrogen-producing microorganism is at least partially to blame for the excess weight, but they acknowledge that further research is required.

Another 2013 study showed that gastric bypass surgery may be effective partially because it alters the gut bacteria, inducing greater weight loss. That study was performed on mice, and when the altered gut bacteria were implanted in the guts of other mice, those mice then lost weight.

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Human connections

While all of this research is compelling, it’s too soon to know how it will all pan out in human trials. “Because of the similarities between regulation of eating behavior in mice and humans, we think that this should work just as well in humans as it does in mice,” Davies says, but first the Food and Drug Administration (FDA) would have to approve such trials.

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For that to happen, more trials in animals are needed to show this treatment can be safe. Studies need to be repeated in young and old mice, as well as mice with compromised immune systems, Davies points out. Additionally, Davies’ team would like to create satiety bacteria with a “kill switch” of sorts, so that if side effects occur, the bacteria can be eliminated without antibiotics, which tend to kill beneficial gut bacteria.

There’s also one other problem when it comes to those human trials: Bacteria are very good at spreading. “Because these are engineered microorganisms, we need to find ways to ensure that the bacteria are not easily transmitted from treated people to others nearby,” Davies says. “We don’t want people to be inadvertently treated with a drug without their knowledge.”

It may be a while before a treatment is available in humans, but at least one thing is clear for now: Unlocking the secrets of the gut may lead us to better health in the future.