NEW YORK >> Anthony Bourdain is not one for activism. Tattooed on his arm in Greek is “I am certain of nothing.”

But at the Tribeca Film Festival, Bourdain has, a little reluctantly, presented a documentary, “Wasted! The Story of Food Waste,” in which he argues passionately against the issue of food waste, from supermarkets to home cooking — even though advocacy of any kind makes him almost physically squeamish.

“Having traveled as much as I do, I constantly go into places thinking one thing only to be shown that I’m wrong and forced by circumstances and exposure to rethink whatever preconceptions I might have had,” Bourdain said in a recent interview. “Activism seems to require a level of certainly and dedication that I’m uncomfortable with. I’m a renter, not a buyer, when it comes to ideologies. I’m a skeptic. I believe very much in skepticism. I don’t ever want to look like a guy with an agenda.”

It’s not that Bourdain is apolitical. The countless meals shared on his years of TV, from “No Reservations” to the soon-returning “Parts Unknown,” are chiefly feasts — both through the food on the plate and the discussions held over them — of larger cultural conversation. Of the traditions kept alive by immigrants. Of the glories of street food. Of the simple power of breaking bread with people from all walks of life.

But standing out front of an issue in today’s ethically charged food world is a step further for Bourdain. So what was it that lured him into combating food waste? A lifetime in which the cooking principle “use everything, waste nothing” was instilled in him, and driven deeper by “one brutal kitchen regime after another.”

“The intent of this film happens to align with something that I feel very strongly from the point of view of just a classically trained cook who came up in a system where the whole idea of waste was abhorrent,” said Bourdain. “The whole story of food as a professional cook is to maximize your profit, to waste as little as possible, to merchandize what is not used in the principle entree. And of course traveling around the world I see again and again and again how circumstances force people to cook really, really well and make the most of the often very little food they have.”

The film is directed by Anna Chai and Nari Kye and executive produced by Bourdain. It’s a tragedy of trash, told colorfully by Chai and Kye.

Some stats: Roughly a third of the food produced for human consumption every year is never eaten. In the U.S., more than 90 percent of wasted food ends up in a landfill, at an annual cost of $1 trillion. The film showcases those using creative solutions to the problem, like a beer called Toast made out of leftover sandwich bread, or a budget grocery store of donated excess foods.

The film also preaches the flavor and thrift of dishes that use typically tossed parts of produce or animals.

“I love tripe, oxtails, cheeks,” said Bourdain. “I love going to a restaurant in Japan where they serve nothing but collars and the meat around the fins. Those are the things that cooks are most passionate about. It’s so funny when you see all of these things that only poor people used to eat now as the hipster dish of the moment.”

Most glaring, though, is the waste of supermarkets where aisles are intended to showcase abundance, even though that means stocking shelves with the intent to not sell all of it.

“In order to have their aisles look a certain way and give an impression of abundance with only the freshest and best, they’ve deemed it necessary to waste tremendous amounts of food that in another situation would be vital to people,” said Bourdain.

“Wasted!” is just the latest in Bourdain’s growing presence in movies. Being a “film nerd,” he says, is “a necessary qualification” for his “Parts Unknown” crew. He recently listed the 10 films that are constant reference points on his shows, from Wong Kar-Wai’s “In the Mood for Love” to Peter Yates’ “The Friends of Eddie Coyle.” The upcoming season, he vows, will pay ode, “if not outright theft,” to David Lean (“Lawrence of Arabia”) when he travels to Oman.

Bourdain last week released “Jeremiah Tower: The Last Magnificent,” a documentary he produced on the storied chef. More films, even fiction ones, could be on the way. “One of the big joys of my life was being on the writing team for the David Simon show ‘Treme,’” Bourdain said. “That was a really fun and exciting experience for me. So that does interest me.”

In the meantime, Bourdain hopes “Wasted” gets people thinking “in a non-didactic perspective.” Then, at least, he can stop playing activist.