It turns out they are protecting their gut flora, he says.

"For the past 10 years doctors have been looking at gut bacteria as something that makes us healthy. If our gut bacteria is not healthy, we cannot be healthy," says Dr Donohoe.

"A lot of what doctors see in their surgeries is just a consequence of altered bacteria playing up." He says entire families can become obese if something in their environment disrupts their gut. There is also much concern around the assertion that gut bacteria imbalance can cause autism, exposed in ABC’s Four Corners recently aired, controversial documentary The Autism Enigma.

"It's not what they eat or some type of moral corruption of the owner of those bugs."

Dr Donohoe is also particularly concerned about the high rate of elective caesarean sections, which may leave babies with inadequate gut flora for years after birth, affecting their weight.

"More research is needed for a solution, but breastfeeding appears to be a healthy and effective way to encourage a broader diversity of gut bacteria in the infant."

As the baby grows, plenty of fresh organic fruit and vegetables in season and minimising grains is the key to a gut-healthy diet, he says.