 Stone serves on the board of several not-for-profit organizations, including Surgeons Over Seas (SOS), which saves lives in developing countries by improving surgical care, and Truth Will Out (TWO), a non-profit think tank and educational organization that defends the LGBT community against anti-gay misinformation.In 2006 Stone, a vegan, met firefighter Rip Esselstyn and the two of them collaborated on the hugely successful book about a low-fat, whole foods, plant-based diet, "The Engine 2 Diet", which in turn was the basis of a product line at Whole Foods Market.They then co-wrote a sequel, "My Beef With Meat."