Peter Ampt, a lecturer in natural resource management at the University of Sydney and a kangaroo meat advocate, said that while some vegetarians loved red meat, they could not justify eating animals that had been poorly treated.
Kangaroos were fair game because they roamed free and were killed humanely with a single shot to the head. The animals were also in plentiful supply, ate only native vegetation and contained no chemicals, he said.
"These people were vegetarians for environmental and ethical reasons, but the more they learned about kangaroo the more they realised it satisfied their ethical and environmental concerns," Mr Ampt said.
"They started eating kangaroo and loved it, then they coined the phrase kangatarians, it was a bit of a joke initially."
Kangaroos emit a fraction of the methane produced by sheep and cows, making them a much better choice for the climate-change conscious, Mr Ampt said.