I remember reading a while ago that one reason about high/low metabolism was based on their microbiome. They fed rats a rich diet for 2 generations and they not

I remember reading a while ago that one reason about high/low metabolism was based on their microbiome. They fed rats a rich diet for 2 generations and they noticed that the new generation got fat even though they were not eating much, they noticed the new genetation was missing a strain of bacteria that their grandfathers had.