If you’ve ever found room for dessert even though you thought you were full, the bacteria in your gut might be to blame. Caltech scientists have shown that mice whose gut microbiome had been disrupted by antibiotics ate far more sugary snacks than normal mice, hinting at a bacterial influence on overeating behaviors.
Scientists are still only beginning to grasp the influence that the huge ecosystem of microbes in the gut has over our general health. By extension, it can even affect our behavior – recent research has shown links between the gut microbiome and personality traits, autism, depression and antisocial activity.
In the new study, the Caltech team investigated how changes in the gut microbiome might affect feeding behaviors – specifically, the kind that might have you dipping back into that bag of M&Ms when you swore you’d stop after the last handful. As it turns out, mice are also partial to these “palatable foods,” those that are eaten for pleasure rather than hunger or nutrition.
In experiments, the team gave one group of mice antibiotics for four weeks to wipe out large chunks of their microbiome, and then compared their feeding behavior to mice that didn’t receive antibiotics. The animals were fed regular mouse chow as a base diet, and were also given the option of high-sugar “dessert” pellets.
While there wasn’t much difference in the amount of chow the two groups ate, mice with disrupted gut bacteria ate about 50% more sugary pellets than control mice, and snacked over longer bursts.
In the next round of tests, the team investigated how much effort the mice would go to for their sugar hit. Rather than just leaving the pellets lying around, the mice needed to push a button to drop them, with subsequent pellets requiring more and more button presses. Mice with normal microbiomes all grew bored after a few button presses, but those given antibiotics would continuously smash that button for a treat.
Intriguingly, when the team restored the mouse microbiome through a fecal transplant, their binge-eating behavior was reduced and their feeding patterns returned to normal. This could have implications for how to treat similar problems in humans.
“The gut microbiome has been shown to influence many behaviors and disease states in mouse models, from sociability and stress to Parkinson's disease,” said Sarkis Mazmanian, lead author of the study. “The recent appreciation that feeding behaviors, driven by motivation, are subject to the composition of the gut microbiome has implications not just to obesity, diabetes, and other metabolic conditions but perhaps to overuse of alcohol, nicotine, or illicit substances that bring pleasure.”
While the microbes that call the gut home are far too numerous for the team to identify the specific culprits behind this phenomenon, they did narrow down the classes based on which antibiotics the mice were given.
“Mice given either ampicillin or vancomycin, but not neomycin or metronidazole, overconsume these high-sucrose pellets compared to controls,” said Mazmanian. “That would suggest that there's some microbe, or some collection of microbes, that is susceptible to either ampicillin or vancomycin, which is responsible for controlling the normal response to the highly palatable foods.”
Of course, results in mice don’t necessarily translate to humans, but the team says that future work could involve studying the feeding habits of people taking oral antibiotics, or investigating the microbiomes of people with a tendency towards sweet treats.
The research was published in the journal Current Biology.
Source: Caltech