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What is food, really?

Food is something that was alive recently, transformed only by methods a home cook recognizes — everything else is an industrial formulation.

13 min read

What is food, really?

TL;DR. The question sounds silly until you walk into a 33,000-SKU supermarket and try to answer it. Three thinkers converge on the same line. Michael Pollan calls most of the supermarket "edible foodlike substances" and offers a great-grandmother test. Carlos Monteiro published a testable category in 2009 — NOVA Group 4 ultra-processed food, defined by industrial ingredients no home cook owns. Robert Lustig collapses the test into one pair: real food has fiber; ultra-processed food has added sugar without it. Kevin Hall's 2019 NIH trial showed processing itself, not the nutrient label, drives overconsumption. The food matrix — physical structure — does most of the actual work. This is a sorting algorithm, not a moral category.

What you'll learn

  • Why "food" needs a working definition before any other dietary question.
  • The four NOVA groups, and why the line between Group 3 and Group 4 is the one that matters.
  • How Pollan, Monteiro, and Lustig converge on the same boundary from different starting points.
  • What the 2019 Hall NIH trial actually proved — and didn't.
  • Why the "food matrix" often matters more than the nutrients on the label.
  • Where the framework gets uncomfortable: NOVA purism, fortified foods, food deserts, edge cases.

The trouble with "food"

The American supermarket carries thirty thousand distinct products. Large stores carry sixty thousand. Roughly seventeen thousand new products launch every year, most engineered from cheap fractions of corn, soy, wheat, and seed oil. The shelves price in five decades of nutritional fashion — low-fat, low-cholesterol, high-fiber, low-sodium, low-carb, high-protein, gluten-free, plant-based — and almost none of those reformulations changed whether the product was actually food.

A specific artifact: a national grocer sells Soft & Smooth Whole Grain White Bread. The phrase is a contradiction, the product is real, and the legal foundation is a 1973 FDA decision. Before then, the 1938 Food, Drug and Cosmetic Act required the word "imitation" on any imitation food. In 1973, after intense lobbying, the FDA replaced that rule with a "not nutritionally inferior" standard — match the recognized nutrients of the original and you can drop the word. That single change unleashed the modern processed-foods aisle. White bread fortified with a token amount of whole grain is now legally indistinguishable from whole-grain bread.

This is the question Pollan opens In Defense of Food with: how did we get to a place where ordinary adults need a 700-page nutrition manual to answer "what should I eat"? His hypothesis is that we lost the definition of food itself. Once you reduce food to its nutrients, you can manufacture any nutrient profile from any ingredients. Margarine, the prototype, has been low-cholesterol, then low-trans-fat, then "made with olive oil" — same product, different fashion. The label moves; the product underneath barely changes. The way out isn't a new nutrient. It's a working definition of food.

Three converging answers

Three writers approached the definitional question from three angles — journalism, epidemiology, biochemistry — and arrived at the same line.

Pollan: edible foodlike substance

Pollan's definition is informal and useful at the shelf. Real food is something your great-grandmother would recognize. It came from a plant, an animal, or a fungus. It has few ingredients, all pronounceable. If you can picture each ingredient growing, being raised, or being butchered, you're holding food. If you can't, you're holding what Pollan calls — borrowing the food industry's own internal vocabulary — an "edible foodlike substance."

Derived heuristics: avoid products with more than five ingredients, ingredients a third-grader can't pronounce, or any health claim on the package. Real food has no lobby — a head of broccoli can't afford an FDA petition. Only industrial formulations need to advertise their nutritional virtues. The loudness of a health claim is a signal of processing, not health.

The seven-word distillation: Eat food. Not too much. Mostly plants. The hardest word, in 2026, is the first.

Monteiro: NOVA Group 4

In 2009, Brazilian researcher Carlos Monteiro and his São Paulo team made the definitional question testable. They were explaining a Brazilian paradox: from 1974 to 2005, household purchases of oil, sugar, and salt fell sharply while obesity exploded. The numbers didn't fit a calorie or macronutrient story. What changed was the proportion of meals coming from industrial formulations rather than home kitchens.

NOVA ignores calories and nutrient grams. It sorts food by what has been done to it. Four groups.

Group 1 — Unprocessed and minimally processed. Fresh and frozen produce, plain rice, dry beans, eggs, raw nuts, milk, plain yogurt, fresh fish and meat. Cleaning, drying, freezing, pasteurizing, grinding, and bagging don't count as processing here.

Group 2 — Culinary ingredients. Olive oil, butter, salt, sugar, honey, vinegar. Substances you cook with, not eat alone. In Monteiro's data, a bag of sugar on the counter is a sign of home cooking — and home cooking correlates with lower obesity rates.

Group 3 — Processed foods. Group 1 plus Group 2, combined using techniques a home cook recognizes. Canned beans. Smoked fish. Real cheese. Salted nuts. Sourdough from flour, water, salt, and a starter.

Group 4 — Ultra-processed foods. Industrial formulations built from substances extracted from food — modified starches, refined-bleached-deodorized seed oils, glucose syrups, protein isolates, maltodextrin — reassembled with substances no kitchen owns: emulsifiers (polysorbate 80, carboxymethylcellulose, DATEM, mono- and diglycerides), gums (xanthan, guar, locust bean), low-calorie sweeteners, color stabilizers, and "natural flavorings." Group 4 is also defined by purpose: shelf-stable, hyperpalatable, brand-able, designed to be eaten in volume.

The line that matters is between Group 3 and Group 4. That is the line that shows up, dose-dependently, across roughly 250 epidemiology papers Chris van Tulleken summarizes in Ultra-Processed People. Every 10 percent rise in the UPF share of a diet correlates with about a 12 percent rise in obesity risk, a 10 percent rise in breast cancer risk, and a 25 percent rise in dementia risk — robust after adjusting for total calories, sugar, salt, fat, fiber, smoking, income, and overall dietary pattern. NOVA-4 is the predictor; nutrients are not.

Fernanda Rauber, on Monteiro's team, gives the sharpest version: Most UPF is not food. It is an industrially produced edible substance.

Lustig: fiber present, sugar absent

Robert Lustig, the UCSF pediatric endocrinologist behind the 2009 "Sugar: The Bitter Truth" lecture, wanted a test a clinician could apply in ten seconds. His operational rule from Metabolical: real food has fiber and does not have added sugar. Ultra-processed food has the inverse.

The biochemistry is direct. Fiber slows glucose absorption, feeds the gut microbiome, generates short-chain fatty acids that signal satiety, and forms a physical scaffold that delays digestion. Strip the fiber and a slow-release carbohydrate becomes a glucose flood; add sugar (especially fructose, which Lustig argues behaves in the liver more like ethanol than glucose) and you fuel the fire. The combination drives de novo lipogenesis, hepatic insulin resistance, and the cluster — type 2 diabetes, fatty liver, hypertension, several cancers, dementia — Lustig groups under metabolic syndrome.

The Lustig, Monteiro, and Pollan rules pick out almost the same products. A whole apple is fibrous, no added sugar — food by all three tests. Apple juice from concentrate, sweetened with apple-juice concentrate, is fiber-stripped with added sugar — not food by any of them, despite a Nutrition Facts panel a parent might glance at and approve.

The Hall trial: this is causal, not correlational

Epidemiology can show two things travel together. It cannot prove causation. For decades, food-industry-funded scientists used that gap to argue the UPF-disease link might be an artifact of income, education, or some other confounder. The argument collapsed in 2019.

Kevin Hall, an NIH senior investigator and originally a NOVA skeptic, ran a controlled-feeding study in the Clinical Center metabolic ward. Twenty adults lived on-site for four weeks. For two weeks they ate an 80-percent-ultra-processed diet; for the other two, an 80-percent-minimally-processed diet. Both were matched for total calories presented, sugar, salt, fat, carbohydrate, fiber, and protein. Volunteers could eat as much as they wanted. Phases were randomized and counterbalanced. The study was published in Cell Metabolism.

On the UPF diet, participants ate about 500 extra calories per day and gained about a pound a week. On the matched whole-food diet, they lost weight. The macronutrients were the same. The only difference was processing. Hall — designing a study he expected to refute Monteiro — produced the strongest piece of causal evidence in the field.

The trial has limits. Twenty people, two weeks per arm, a metabolic-ward population isn't a free-living one. The exact mechanism — softness, calorie density, eating speed, flavor-nutrient mismatch, microbiome effects — is still being worked out. But the effect is large, in the predicted direction, and emerged from a skeptic. If you remember one nutrition study from this era, this is it.

Why "the food matrix" matters

Anthony Fardet, a French food scientist at Université Clermont Auvergne, named what the Nutrition Facts panel keeps missing: the food matrix. Food is more than the sum of its nutrients. Physical structure — fiber scaffolding, intact cell walls, embedded fats, water binding — controls how fast molecules reach the bloodstream, how the gut responds, and how the brain reads satiety.

A 1977 study compared whole apples, apple purée, and apple juice — same sugars and fiber on paper, three different blood-glucose curves and three different satiety responses. Whole apple: slow rise, lasting fullness. Purée: faster rise. Juice: spike, crash, hunger an hour later. Same fruit, three matrices, three different metabolic outcomes.

The pattern generalizes. Steel-cut oats, rolled oats, and instant oatmeal carry the same macronutrients but produce sharply different glycemic responses. Whole almonds and almond flour share a nutrition label and absorb fat at different rates. Sourdough and sliced supermarket bread can match on the label and diverge inside a person. Nutrient-label thinking counts ingredients and ignores architecture.

NOVA Group 4 is, in practice, a category whose matrix has been engineered for speed — fast to eat, fast to absorb, fast to leave the gut and re-trigger hunger. That is what the Hall study isolated. The matrix, not the nutrients, drove the 500 calories.

What this means for "ultra-processed" as a category

"Junk food" is a moralized category. It mixes Twinkies and frozen broccoli depending on the speaker's politics. NOVA Group 4 is not that. It is a processing category, applied to ingredient lists and production methods, with predictable boundary behavior.

Frozen broccoli is Group 1. Dried pasta is Group 1. Canned tomatoes are Group 1. Plain Greek yogurt is Group 1. Real cheddar, smoked salmon, and bakery sourdough are Group 3. A "lower-sugar" sweetened cereal with reduced sodium and added fiber is still Group 4, because reformulation doesn't move a product between groups — the substances and processes that defined it are still there.

The category also tracks marketing. Almost every product carrying a front-of-pack claim — "supports immunity," "good source of fiber," "made with real fruit," "heart-healthy whole grains" — is Group 4. Real food has nothing to prove on the front of the box.

The nutritionism trap

Pollan's word for the operating system of the last fifty years is nutritionism: the ideology that food equals the sum of its nutrients. Four hidden axioms — nutrients are what matter, nutrients are invisible so experts must interpret them, the purpose of eating is bodily health, and nutrients divide into heroes and villains. Once an ideology is dominant, it becomes weather: invisible while it reigns.

Nutritionism has a birthday. In 1977, the McGovern Senate Committee drafted Dietary Goals telling Americans to eat less meat. The beef and dairy lobbies pushed back hard. McGovern, a senator from cattle-ranching South Dakota, blinked. The recommendation was rewritten as choose meats, poultry, and fish that will reduce saturated fat intake. With that linguistic move, U.S. dietary advice switched from naming foods to naming nutrients. Nutrients have no constituency. The food industry, which can reformulate any product around any nutrient fashion, was handed a permanent license to invent new categories of processed product.

Every fad since — low-fat, low-cholesterol, low-trans-fat, low-sodium, low-carb, high-protein, high-fiber, plant-based — has played by nutritionism's rules. Each produced its own reformulated supermarket aisle. None reversed the chronic-disease trend. The fix isn't a better nutrient. It's escaping the framework.

Three honest nuances

None of this should be religion. Three places where it gets uncomfortable.

Some ultra-processed food is genuinely useful. Fortified infant formula for non-breastfed babies, vitamin-fortified flour that prevents neural tube defects, oral rehydration solutions, shelf-stable disaster-relief foods — all NOVA-4. The category predicts population-level harm; it isn't a verdict on any single product. Don't be a NOVA purist.

Access and income matter; the framework should advocate, not gatekeep. Tens of millions of Americans live in environments where Group 4 is functionally the only food within walking distance. Calling that personal failure is the wrong move. NOVA is most useful as a policy lever — warning labels, marketing restrictions on children's products, school-food rules, sugary-drink taxes — not as a shibboleth at the checkout.

The boundary is real, but a few products are debatable. Plain Greek yogurt and fruit-on-the-bottom yogurt sit on opposite sides of a real line. Minimally processed deli meats, some plant-based milks, and certain artisanal items reformulated for shelf life sit closer to the boundary. The arguments at the edges don't undermine the framework — they're the friction every useful category produces.

Frequently asked questions

If NOVA is testable, why don't dietary guidelines use it?

Brazil's 2015 dietary guidelines use it explicitly. Several Latin American countries followed. U.S. and U.K. guidelines do not, despite NOVA's adoption by FAO and PAHO. The structural answer is industry capture: U.S. guidelines are written by a committee with extensive food-industry funding, then softened by an interagency process. Marion Nestle documents this in What to Eat Now (2025). Naming "ultra-processed food" as a problem implicates most of the U.S. food economy.

What's the difference between "processed" and "ultra-processed"?

"Processed" is an everyday word covering everything from a cube of cheese to a Dorito. NOVA splits it. Group 3 uses methods and substances a home kitchen owns — salt, fermentation, smoke, oil, heat, time. Group 4 uses extracted fractions and substances no kitchen has. The harm signal sits on Group 4.

Is bread NOVA-4?

Depends. A four-ingredient bakery loaf (flour, water, salt, yeast or starter) is Group 3. A supermarket sliced loaf with mono- and diglycerides, DATEM, sodium stearoyl lactylate, soy lecithin, calcium propionate, and added sugars is Group 4. Same shelf, opposite categories.

Are plant milks always NOVA-4?

Almost always. Typical lists include canola or sunflower oil, gellan gum, dipotassium phosphate, often added sugars and flavors. A handful of brands sell minimally processed versions (water, nuts, salt). Plain dairy milk is Group 1.

How is the Hall trial different from previous obesity research?

Most prior research was observational (correlation, with confounders) or focused on isolated nutrients (low-fat vs. low-carb, low-glycemic vs. high-glycemic). Hall matched the nutrients and varied the processing — isolating processing as a causal variable, which no previous controlled-feeding study had done.

Doesn't the food-matrix concept just mean "whole foods are better"?

Yes, with mechanism. "Whole foods are better" is a slogan; the food-matrix literature explains why — fiber scaffolding, intact cell walls, water binding, and embedded fats produce slower absorption, longer satiety, and different microbiome signals. Mechanism turns a heuristic into a testable claim.

Is nutritionism the same as nutrition science?

No. Nutrition science is the empirical study of how food affects bodies. Nutritionism is an ideology that treats food as nothing but its nutrients — and uses that reduction to license endless reformulation. Pollan's critique is of the ideology, not the science. Good research (including the Hall trial) is dismantling nutritionism from inside.

Is a Beyond Meat or Impossible Burger NOVA-4?

Yes. The ingredient list — pea or soy protein isolate, refined coconut and canola oil, methylcellulose, natural flavors, modified food starch — is textbook Group 4. "Plant-based" doesn't mean "real food." A bowl of lentils is plant-based; a Beyond Burger is a plant-derived industrial formulation.

Sources

  1. Pollan, M. In Defense of Food: An Eater's Manifesto. Penguin Press, 2008. Nutritionism, the 1973 imitation-rule repeal, the great-grandmother test, the seven-word manifesto.
  2. Pollan, M. Food Rules: An Eater's Manual. Penguin, 2009. "If it came from a plant, eat it; if it was made in a plant, don't."
  3. Monteiro, C. A., Levy, R. B., Claro, R. M., Castro, I. R. R., & Cannon, G. (2010). "A new classification of foods based on the extent and purpose of their processing." Cadernos de Saúde Pública, 26(11), 2039–2049. doi: 10.1590/S0102-311X2010001100005. (Earlier formulation: Monteiro 2009, Public Health Nutrition, doi: 10.1017/S1368980009005291.)
  4. Hall, K. D., Ayuketah, A., Brychta, R., et al. (2019). "Ultra-processed diets cause excess calorie intake and weight gain: an inpatient randomized controlled trial of ad libitum food intake." Cell Metabolism, 30(1), 67–77.e3. doi: 10.1016/j.cmet.2019.05.008.
  5. van Tulleken, C. Ultra-Processed People. W. W. Norton, 2023. NOVA-4 mechanisms, the Hall trial reception, the additive vocabulary, the Rauber line.
  6. Lustig, R. H. Metabolical: The Lure and the Lies of Processed Food, Nutrition, and Modern Medicine. Harper Wave, 2021. "Protect the liver, feed the gut"; fiber-present, sugar-absent as the operational test.
  7. Fardet, A. (2016). "Minimally processed foods are more satiating and less hyperglycemic than ultra-processed foods: a preliminary study with 98 ready-to-eat foods." Food & Function, 7(5), 2338–2346. The food-matrix concept.
  8. Schatzker, M. The Dorito Effect. Simon & Schuster, 2015. Why flavor became something engineered onto bland industrial substrate, and what that does to appetite.
  9. Nestle, M. What to Eat Now. Farrar, Straus and Giroux, 2025. Supermarket politics, the U.S. guidelines process, why NOVA hasn't made it into U.S. policy.

Related modules

  • ← B2: Real food vs. edible foodlike substance (beginner)
  • C2: Inside your cells (mitochondria, ATP, insulin) →
  • C8: The ultra-processed food problem →

Related glossary terms