Work to find the magic bullet for weight loss has led to some unexpected places.

Most recently, researchers have focused on whether harvesting the gut bacteria from thin people’s poop and transplanting it in those who are seriously overweight might do the trick.

Fecal transplant has been a strange area of research, pioneered first for people suffering from the chronic, hard-to-treat gastrointestinal infection, C. difficile. The first tests involved glass jars in paper bags, blenders, and enemas.

No more.

A Food and Drug Administration-approved clinical trial led by Harvard researchers will provide freeze-dried gut bacteria from healthy, lean volunteers to obese study participants in double-lined capsules to see if the bacteria colonize in the participants’ guts and lead to weight loss.

"The pills are odorless, tasteless, and double-encapsulated to ensure they will not release until they reach the right location in the large intestine," lead researcher Dr. Elaine Yu told the New York Daily News.

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Caged Mice Led to Discovery

Gut bacteria was first linked to weight thanks to the disgusting habits of lab mice. Mice that had been bred to be obese were housed with healthy mice.

When mice share space, they eat each other’s poop. The obese mice became leaner with no change to their access to food.

Later, a case study of Rhode Island woman who underwent a fecal transplant to treat C. diff suggested that the bacterial transfer could affect metabolism in humans, too. The fecal donor was obese and though the recipient recovered from the infection after the transplant, she went on to become obese herself.

The events suggested that there may be something in gut bacterial profiles that predisposes people to being fat or thin.

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Transplants Are Too Extreme

Still, fecal transplants using enemas are too extreme for broad medical use.

Scientists found in 2014 that patients with a C. diff infection did not get sick and, in fact, often recovered when they were given freeze-dried fecal matter in a capsule.

Yu and her colleagues now hope that capsules will also safely and effectively deliver the bacteria that facilitate better metabolic health.

Even in its newer, more user-friendly delivery system, fecal microbiota transplantation (FMT) still has a ways to go before it ceases to be an experimental approach.

Researchers have yet to nail down which types of bacteria do what, making every clinical trial something of a, yes, crapshoot.

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