A focus on a food’s level of processing can lead to odd conclusions, however. Julie Hess, a research nutritionist at the U.S. Department of Agriculture, has pointed out that “ultra-processed food” puts canned kidney beans and gummy bears into the same category. Processing also has some benefits. It prevents food from going bad or being contaminated during storage and transport; it allows more people to eat convenient and varied meals, even when particular foods are not in season; and it helps the world feed a growing population. Walter Willett, a Harvard professor who may be the most cited nutrition researcher in the world, argues that studies like Hall’s are “worse than worthless—they’re misleading.” (He prefers to focus on the combinations of foods that people eat over time, and advocates for plant-based whole foods and the Mediterranean diet.)
While Raineri was having breakfast, I went down to a “metabolic kitchen” in the basement, which looked like a chemistry lab in the back of a restaurant. Raineri’s lunch and dinner were already being prepared; chicken breasts sizzled on a stovetop, and the smell of fried potatoes made my stomach growl. “A lot of chefs like to be creative,” Merel Kozlosky, a woman in a blue baseball cap who serves as the kitchen’s director, told me. “What we’re looking for is people who’re meticulous about following instructions.”
Hall and his colleagues had developed exacting protocols so that less-processed meals would closely match ultra-processed meals in terms of nutrients like salt, sugar, protein, and fat. This was meant to isolate the effect of processing. Tomato slices and lettuce leaves sat on a scale, which weighed food to the nearest tenth of a gram; a large stopwatch, for keeping track of cooking times, ticked nearby. Instructions on a clipboard explained how much Pacific Foods vegetable broth to add to soups A1 through E1, whose salt contents ranged from 0.39 grams to 5.61 grams.
I asked a tall, brown-haired cook which diet he most likes to prepare. “Preparing a day’s worth of ultra-processed meals might take an hour,” he said. “Unprocessed meals could take three or four times as long.” He brought his knife down forcefully, cleaving a carrot in two, and continued: “If I’m swamped, I’d rather make the ultra-processed menu. But if I had to pick one to eat for the rest of my life? Unprocessed, no question.”
A central question of the study is whether, consciously or unconsciously, participants eat more when they’re given ultra-processed foods—and, if so, why. This is why participants are offered such immense portions and can stop whenever they want. At one point, Kozlosky pulled a tray out of a commercial refrigerator. The meal looked as though it could feed a family of four: a tub of salad, a bowl of dressing, a container of beans, a cup of salsa, some shredded cheese, a wild-rice blend, and two pitchers of seltzer. After a meal, researchers weigh each dish to see how much has been eaten.
“Is this processed or unprocessed?” I asked.
Kozlosky smiled. “Ultra-processed,” she said. “Lots of participants can’t tell the difference.”
The term “ultra-processed food” was introduced by a Brazilian epidemiologist named Carlos Monteiro. In the early seventies, Monteiro was a primary-care doctor in the Ribeira Valley, an impoverished part of rural Brazil, and he treated many plantation workers with swollen bellies, stunted growth, and exhaustion. He started to think that they needed better food, in larger quantities, more than they needed medicine. He relocated to São Paulo, hoping to study malnutrition. Then he learned that around a million Brazilians were growing obese each year. Strangely, a shrinking number of people were buying ingredients that doctors blamed for the obesity epidemic, such as salt, sugar, and oil. The paradox troubled him.