Credit: Robert Ascroft / Courtesy Rolex

About four years ago, Oscar-winning director James Cameron began an all-vegan diet. A long-time environmental advocate, Cameron made the change explicitly to help save the planet, namely by lowering his carbon footprint, but the record-setting deep-sea diver also found that it also drastically improved his health, what he calls "a win-win." Here, in his own words, is why he has kept it up.

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The great thing about this as a solution for climate change — one of a number of solutions that we need — is that it's a win-win. You're going to be healthier, you're going to live longer, you're going to look better. You're going to have fewer zits. You're going to be slimmer. You're going to radiate health. You're going to have a better sex drive. That's what shifting away from meat and dairy does.

My whole family did this, and we're doing spectacularly well from a health standpoint. I have not had a single sniffle, not a flu, not a cold, nothing that's taken me offline as much as an hour in three and a half years. Now, that's either the biggest, craziest, statistical anomaly in history, or there's a strong causal relationship with this profound diet change that we did.

Culture, Diet, and Longevity
The blue zones [five regions around the world that researchers have identified as having the highest concentrations of centenarians in the world] prove this diet works. You have people from separate cultures who aren't related to each other in any way, but what they all have in common is they eat very little meat and they eat diets high in plants. They also do other things like they move naturally all day long. They don't go to a gym three times a week for an hour and think that that's going to offset the 12 hours of sloth sitting at a desk in front of a screen or sitting at home playing video games. So there's a whole constellation of things that make you a centenarian in these blue zones, but the one resounding common element is they eat mostly plants, and I took this to heart three and a half years ago and went 100 percent plant-based.

The Problem with Paleo
People want that assurance because they hear about the Paleo diet and the Atkin's diet, and you're supposed to eat a big stack of pork chops every day, so there's a lot of controversy out there. If you've got the appetite for it, read The China Study, which is a big thick book, or get the download Forks Over Knives, which is a simple short documentary that spells out the health issues and how it was discovered that plant-based eating is so much better for you.

Easing Into It
One way to go vegan is to slowly cut down on your meat consumption and learn how to either source or make good, tasty plant-based meals, and that takes a little bit of time. There's another technique that I recommend, which is to go cold turkey for a short period of time. Just go 100 percent plant-based for 21 days. You'll have to stock up on vegetables and get a cookbook or buy some frozen plant-based meals at the grocery store. We went cold turkey and never looked back. But I said to my wife when we agreed to do this that I hold the right to have a prime rib or a T-bone steak if I want to. And what I found was after a month I just simply didn't want it. I never wanted it again, because your brain reprograms itself.

—As told to John Gaudiosi