Environmental and food advocate Michael Pollan has the answer to being healthy: eat food, not too much and more plants than meat.
In the above video, he talks about the difficulty of embracing these practices in a modern, western society, because most of what we are served is what he calls "edible, food-like substances."
In a blog piece on The Huffington Post last year, he described some of the "Food Rules" which guide people on eating "real food" -- this includes avoiding products you see advertised on television. He adds in the above video, "If it has more than five ingredients, it's probably not food. Or if it has ingredients that your third grader can't pronounce, it's probably not food."
In New York Times piece in October, Pollan said the current food system is "unsustainable" and will likely look very different in 100 years. As an example, he says that as the demand for humanely raised meat has grown in the last few years, the industry has responded, with food chains like McDonald's and Chipotle working to make the switch.
His last word of advice: "Cook for yourself, it's going to be healthier than what you're buying."