Matthieu Ricard is a Tibetan Buddhist monk and an expert on happiness.

He's author of Happiness: A Guide to Developing Life's Most Important Skill, and has been labelled the 'happiest man in the world', after neuroscientists discovered that, while meditating on compassion, Ricard’s brain produces a level of gamma waves "never reported before in the neuroscience literature."

Ricard has now teamed up with People for the Ethical Treatment of Animals to urge people to adopt a vegan lifestyle - suggesting it is the only why to find true happiness in life.

“I am extremely concerned by the fate of the 8 million other species who share this world with us, and who, like us, wish to avoid suffering and live out their lives," says Ricard in a video shared on PETA's Facebook page.

Warning: this video features graphic images of animals being killed for meat