Paul McCartney says a vegetarian lifestyle is both humane and energy efficient. 

Appearing last week on BBC's radio'ss Food Program, the ex-Beatle said he was first exposed to a meat-free diet while studying with the Maharishi in India. But the bland dishes, far from the delicious curries found in big cities, didn't impress him.

His watershed moment came at his farm in Scotland. While eating with his first wife Linda, they watched lambs running near the house, the realization they were sitting down to leg of lamb -- and seeing "the sheer vibrancy of a new life" -- caused them to give up meat.

Paul McCartney recalled the incident that caused he and Linda to give up eating meat.

"So we were eating a normal traditional meat diet. But it was really just one day, when we happened to be on our farm in Scotland and it was lambing season. And we were looking out of the window, watching the lambs playing around. Just the sheer vibrancy of a new life. And then we looked and we thought, 'Oh, we're eating leg of lamb.' And it just became obvious, and we looked at each other and said, 'Should we maybe try not doing this?' And so that was when we became vegetarian."

In recent years he has advocated for meat-free Mondays and the reduction of meat in diets. The inefficiency of growing grains to feed animals bothers Sir Paul, as does the amount of fuel needed for -- and the resulting pollution from -- raising livestock. That's led to testifying before groups advocating changing dietary habits. He feels the vegetarian lifestyle might even make a dent in amount of starvation in third-world areas.