The team's mouse studies also suggested that the ALK gene instructs fat tissues to burn more fat from food.

O'Rahilly described the animal studies as "well done" but noted that the genetic variation that was associated with lower body mass index in the Estonia biobank was "modest" and not as robust as many experts in the field would accept as "definitive."

However, he said that previous studies in much larger populations have shown a suggestive, but not strong, signal of an association with body weight in that area of the genome, and it was unlikely that the variation would be unique to Estonians.

Penninger said that treatments targeting the gene might help scientists fight obesity in the future.

"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," Penninger said.