You were right: those friends eating whatever they want, never exercising, yet never gaining any weight - they are not like us.
They are genetically different, as stated in a study recently published in the journal Cell by an international team lead by Dr. Josef Penninger from the University of British Columbia, Canada. The scientists claim they have identified a genetic variant unique to thin individuals in a gene known as the ALK gene, responsible for producing a protein called Anaplastic Lymphoma Kinase. A mutated form of the ALK gene is also involved in tumoral growth. But the mutation observed this time does not cause cancer or other illnesses, but instead allows the carrying subjects to stay thin no matter what they eat or how much they exercise. If they exercise.
“We all know these people, who can eat whatever they want, they don’t exercise, but they just don’t gain weight. They make up around one per cent of the population. We wanted to understand why. Most researchers study obesity and the genetics of obesity. We just turned it around and studied thinness, thereby starting a new field of research. We looked at the genetic maps of people with a BMI below 18 and compared them with those of people of normal weight and found the [mutation] that correlated with being super skinny” -- Dr. Josef Penninger, Life Sciences Institute Director at the University of British Columbia, Canada
Then they turned to mice and flies and studied how inhibiting the ALK gene affects them. And they were affected big time. When Penninger’s team deleted the ALK gene in flies and mice, both were resistant to diet-induced obesity. Despite consuming the same diet and having the same activity level, mice without ALK weighed less and had less body fat.
What's next? More studies, of course. But in the (not so) long run, we might finally have a potent weapon against obesity. ALK inhibitors are currently used in cancer treatments and if the link between obesity and ALK is confirmed on humans, we might readily use the same treatments for reducing or even eliminating obesity.
"If you think about it, it's realistic that we could shut down ALK and reduce ALK function to see if we did stay skinny. ALK inhibitors are used in cancer treatments already. It's targetable. We could possibly inhibit ALK, and we actually will try to do this in the future." -- Dr. Josef Penninger