Researchers have fund that, in the words of the New York Times, “The trillions of bacteria that live in the gut — helping digest foods, making some vitamins, making amino acids — may help determine if a person is fat or thin.” Scientists were puzzled by pairs of human twins in which one was obese and other other lean. They took “gut bacteria” from both of them and put them, separately, into mice. The mice with bacteria from fat twins grew fat; those that got bacteria from lean twins stayed lean.
And then … they did more. They created mouse food that was “healthy” — with fruits and vegetables and low fats — and that was less healthy — with no fruits or vegetables and with lots of fat, and they fed them to the mice with the twins’ bacteria. The result: The fat mice that got food high in fat and low in fruits and vegetables kept the gut bacteria from the fat twins and remained fat. The thin twins’ gut bacteria took over only when the mice got pellets that were rich in fruits and vegetables and low in fat.