A binge-eating fish could help explain why some humans over indulge at dinnertime.
The blind albino fish live in remote caves in north-eastern Mexico where food only becomes available about once a year when it is swept in by floods.
Over hundreds of thousands of years, the cave fish have adapted to the darkness by losing their eyes, as well as learning how to resist starvation by binge eating in times of plenty.
Understanding how these fish have evolved to be fat might help experts explain why some people are obese.
Professor Clifford Tabin, the study’s lead researcher at Harvard Medical School, said: ‘We all know that people have different metabolisms that lead to their gaining weight under different amounts of eating.
‘The work with the cave fish gives us an example in a natural setting of why and how metabolisms evolved to be different.
‘Some of the mechanisms we see in the fish may well have implications for human metabolism and therefore human health.’
Like humans with inherited obesity, most of the fish were found to have mutations in the MC4R gene, known to be at the heart of appetite regulation.
The gene is regulated by leptin, an appetite-suppressing hormone and insulin in the human brain.
In laboratory tests, mice lacking MC4R were found to be severely obese and constantly hungry.
Tests showed that after two months without food, Mexican cave fish lost half as much weight as another version of the same species that lives above ground.
After three months, the cave fish continued to thrive, while their surface-dwelling cousins began to starve and die.
Co-author Dr Nicolas Rohner, a researcher in Prof Tabin’s laboratory, said: ‘These fish are very, very fat – much fatter than surface fish.
‘And although they are active, their metabolism is slower.’
The study, published in the journal PNAS, showed that MC4R activity was reduced in the cave fish, taking the brakes off appetite suppression.
Source: Could binge-eating FISH shed light on human obesity? | Daily Mail Online