If you've ever been jealous of people who can eat whatever they want without putting on weight, here's some good news to consume.
Scientists think they've figured out how they do it, and might soon have a way for the rest of us to pig out without fear.
Scientists in Canada looked at a genetic database of more than 47,000 people and found a genetic mutation only present in skinny people - the thinnest 1 percent.
The mutation is the absence of the ALK gene.
To test whether the mutation is really behind their thinness, or whether it's just a coincidence, the scientists decided to cut the equivalent gene out of mice and flies.
University of British Columbia genetics Josef Penninger, who led the study, told The AM Show on Monday it worked.
"We basically did genetic engineering and cut out the gene from the genome of the mouse, and created a mouse that stayed skinny even if we gave the mouse a hamburger diet."
The brain essentially orders the body to burn more calories when the gene is absent than when it's there.
"We know the same gene is associated with thinness in humans... the next step really is to see how this can be changed [in humans]. We really have to study how certain types of food influence this gene."
Prof Penninger said they're also looking into traditional Chinese medicine and diets, which seem to suppress obesity, to see if they're somehow linked to the ALK gene. If they're successful, one day you might be able to buy a pill or treatment that suppresses the gene, making it easier to control your weight.
"We're homing in on them to see how they influence this gene. If we find this, we can develop something much, much faster."
But don't think that means you'll be free to live a couch potato life.
"This doesn't take away that we have a healthy lifestyle and do sports," said Prof Penninger. "It's just part of the equation."
The research was published last week in journal Cell Press.