“Eat food. Not too much. Mostly plants.”

Michael Pollan chose this mantra to begin his new book, “In Defense of Food: An Eater’s Manifesto.” For good measure, he slapped it on the cover, too.

It seems simple enough at first reading — isn’t everything we eat food? But Pollan distinguishes between yogurt and Go-gurt, between foods our grandmothers would recognize and the “foodlike products” now found on grocery store shelves.

In his earlier book, “The Omnivore’s Dilemma,” Pollan detailed the industrial processes that produce most of what Americans now eat, focusing on massive cornfields, slaughterhouses and chemical plants. In “In Defense of Food,” he blames the shift away from real food on the prevalence of food science and “nutritionism” — an obsession with invisible molecules of cholesterol and carbohydrates rather than recognizable foods.

Americans once learned what to eat by watching what their mothers prepared. Those menus were largely imported by immigrants from their home countries. So Pollan’s grandparents prepared blintzes, knishes and vegetables cooked with lashings of rendered chicken fat — all dishes derived from the cuisine of Russia and Eastern Europe.

But food faddism, bolstered by faulty science, undermined the authority of those traditional food cultures. Pollan’s grandparents’ cuisine was laden with saturated fats; when scientists identified saturated fats as a contributing factor to heart disease, subsequent generations were cut off from their inherited food culture. Logically, they turned to scientists to answer the question: “What should I eat?”

Pollan is especially convincing in demonstrating how scientists’ quest for a single molecule to explain human health — complicated by the political influence of the agribusiness lobby — led to a series of misleading and ultimately unhealthy dietary rules. That same “discovery” of the pernicious effects of saturated fats created a market for margarine as a less tasty, but supposedly healthier, replacement for butter. Decades later, margarine’s trans-fats have come under assault by everyone from New York City’s mayor to the food companies themselves.

The first two-thirds of Pollan’s book are dedicated to explaining and expanding on the prevalence of nutritionism. He guides the reader through the various “magic bullets” that at one point or another were supposed to explain the problems with the “Western diet” — the combination of meats and refined carbohydrates that breeds illness in every new population that adopts it. We went from avoiding fat in the low-fat era to embracing it during Atkins. And now, Pollan suggests, omega-3 fatty acids (found in fish) are going be the next major food trend: “Omega-3 fatty acids are poised to become the oat bran of our time as food scientists rush to microencapsulate fish and algae oil and blast it into such formerly all-terrestrial foods as bread and pasta, milk and yogurt and cheese, all of which will soon, you can be sure, spout fishy new health claims.”

Pollan is deeply skeptical of such health claims, which though purportedly FDA-approved may in fact be meaningless. He cites the following label appended to bottles of corn oil: “Very limited and preliminary scientific evidence suggests that eating about one tablespoon (16 grams) of corn oil daily may reduce the risk of heart disease due to the unsaturated fat content in corn oil … [The] FDA concludes that there is little scientific evidence supporting this claim.”

Guess which sentence is in small print.

But if we can’t listen to the FDA, and we can’t listen to scientists, who should we trust to tell us what to eat?

That’s where the final third of Pollan’s book comes in. The first chunk of the book (on nutritionism and the problems with food science) grew out of a cover story he wrote last year for The New York Times Magazine. For the book, he added a few dozen pages of his own prescriptions for eating, which can be boiled down to the seven words with which the book (and this review) begins.

“In Defense of Food” is not a diet manual: it’s a manifesto for eaters, not trying-not-to-eaters. But it’s surely no coincidence that Pollan’s book was released on Jan. 1, along with a wave of other diet books, just in time for the New Year’s Resolutionists. Obesity (and its related ailments) is the major health crisis that Pollan links to nutritionism and the Western diet. And his recommendations have much in common with conventional diet wisdom: eat more slowly, so that you can tell when you’re full; don’t snack; choose filling fruits and vegetables over energy-dense pasta and meat. At the same time, he dismisses advertisers’ health claims and the American obsession with the nutrient of the hour. Along with those diet-minded suggestions, Pollan also jumps on last summer’s “locavore” bandwagon with recommendations to shop at farmer’s markets and eat organic and local when possible.

But the relatively cliched quality of his own advice does not take much away from the interest of the book as a whole. “In Defense of Food” is a thoughtful and provocative examination of our contemporary food “culture.” And if it makes us worry less and savor more, all the better.