Fat Fish and Obesity: Binge Eating Gene Shared With Humans

It may sound utterly outrageous, but experts are now arguing that some very fat and blind cave fish may hold the key to understanding humanity's obesity problem. The same genes that apparently help these fish feast without constraint also happens to be one of the strongest genetic drivers for inherited obesity ever seen.

That's at least according to a study recently published in the Proceedings of the National Academy of Science (PNAS), which details how blind cavefish (Astyanax mexikanus) found in the subterranean habitats of in northeastern Mexico may have adapted to favor binge eating over what is seen a traditionally healthy restraint. A video can be viewed below. Jump to video.

Living in lightless and isolated caves, these fish have heavily evolved to make the best of their home - a place that can often lack proper sources of food for months on end. Past work has revealed that during times when food is scarce, these fish can become masters of fasting - entering what can only be described as a hibernation-like state even while remaining awake and alert.

Researchers had hoped that polar bears were capable of a similar state - allowing them to adequately switch over to a nomadic lifestyle. You can read more about that here.

Then, when seasonal floods bring fresh waters and abundant food into the caves, these fish turn their dieting habit completely on its head. Suddenly they gorge themselves without restraint, binge-eating until they are fit to burst. (Scroll to read on...)

As a consequence, these fish become "very, very fat - much fatter than surface fish," researcher Nicolas Rohner, co-first author of the study, said in a statement.

"And although they are active," he added, "their metabolism is slower," meaning these fish are able to maintain immense fat recovers for a very long time - well after all their newfound food is gone.

Investigating the mechanism of this remarkable binge-eating, Rhoner and his colleagues quickly found that these cave fish sport heavily mutated versions of MC4R, a gene known to be regulated by insulin and an appetite-suppressing hormone called leptin.

"It's one of the key components in maintaining your energy balance," co-first author Ariel Aspiras explained. "When people try to diet or change how much they weigh, there are regulators in your brain that try to keep you at your current body weight. MC4R is one of them."

It is suspected that for the fish, these mutations are rendering this regulator near-useless, allowing the fish to gorge themselves the way they do without hesitation. And stunningly, one of the cave fish MC4R mutations proved identical to a mutation seen in humans. Past work has recognized this shared mutation as the most common single-gene cause of inherited obesity.

But while it's easy enough to understand why these cave fish want to get as heavy as possible before their next fasting season, experts still don't understand why binge-eating mutations have persisted in humanity.

"That's something that bothers me a lot - that we have to fight against this urge to eat and drink sweet and fatty things all the time and that it's because of our evolutionary history," Rhoner added. "The possibility that we can find out why that is, perhaps by using these cavefish as a model system, makes me confident that one day we will find a way to resist that urge." (Scroll to read on...)

Interestingly, this is not unlike the Drunken Monkey Theory, which suggests humanity's past has led to a genetic predisposition for alcoholism. You can read more about that in the third part of an exclusive NWN feature, found here.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

- follow Brian on Twitter @BS_ButNoBS