My mother-in-law used to be a fairly typical American. At age 64, she was a touch overweight, a bit inactive, and largely dependent on statins to keep her cholesterol in check. Then, last year, she went vegan after learning about Bill Clinton’s now-famous foray into plant-based eating. Within six months, she dropped 35 pounds, had more energy, and no longer needed Lipitor. That one decision likely increased the number of years she’ll have to spend with her grandkids, too, because research shows that a vegetarian diet increases lifespan.

By abstaining from all animal products—including meat, poultry, fish, eggs, dairy, gelatin, and honey—my mother-in-law also directly and powerfully benefits the planet. Think your neighbor’s SUV is bad news? Animal agriculture’s climate footprint is greater than that of all the world’s cars, buses, boats, and trains combined, according to the Food and Agriculture Organization of the United Nations.

Livestock emit massive amounts of greenhouse gases, and they’re a leading player in deforestation, biodiversity reduction, and water pollution. A recent study published in Environmental Research Letters suggests that halving meat consumption in developed countries is the only way to stabilize emissions of the greenhouse gas nitrous oxide. Reducing meat intake is so critical, in fact, the World Wildlife Fund calls it “an environmental imperative.” And don’t get us started on the inhumane and polluting industrial-food systems known as concentrated animal feeding operations (CAFOs).

If you’re considering making the switch to this healthy and environmentally responsible way of eating, here are some facts about going vegan.