I was gaining weight very rapidly and read about the idea of restricting carbohydrates as an alternative to going hungry. I had a big appetite, so that was the only thing I would even consider.
When I meet vegetarians who might have diabetes, pre-diabetes or massive obesity, I tell them they would be better off if they gave up their Vegetarianism.
It's so logical and so simple. Fat is the backup fuel system. The role it plays in the body is that when there's no carbohydrate around, fat will become the primary energy fuel. That's pretty well known.