It’s been five years since nutrition scientist Kevin Hall made a startling discovery that changed the way we view ultra-processed foods.
Hall put 20 people — 10 women and 10 men — into a tightly controlled metabolic ward at the National Institutes of Health and watched what they ate for a month. Half the time, the study subjects were given only fresh, unprocessed foods, like Greek yogurt with fruit and nuts for breakfast, or a broccoli and beef stir-fry for dinner. For the other half of the month, they were offered the same amount of calories and key nutrients every day, but from factory foods like turkey bacon, English muffins, and chicken nuggets.
At the end of the month, the evidence was conclusive and damning: people who eat ultra-processed diets consume more calories, and gain more weight, without trying. It was the first randomized controlled study of its kind, and it changed the way we view ultra-processed foods. “Whole” food and “plant-based” diets took off, and “clean” eating has become trendier than ever, as people try to aggressively limit their intake of packaged goods.
But discovering that people eat about 500 extra calories per day on an ultra-processed diet didn’t convince Hall that convenience foods should be universally shunned.
“What we’re trying to figure out is, very specifically, what is it about ultra-processed foods that seems to drive over-consumption and weight gain?” Hall told Business Insider.
He wants to understand precisely why ultra-processed foods do what they do and what—if anything—we can do to make them healthier.
“If you can avoid them, that’s wonderful, but most people can’t,” he said.
So, for over a year now, he’s methodically invited 18 volunteers back to his special Bethesda, Maryland lab, to try out some newly formulated ultra-processed meals. By the time the study’s over, in 2025, at least 36 people will have tried out the reformulated foods, and been monitored for weight gain, as well as hormonal changes.
Hall’s testing out two big ideas, hoping that perhaps by baking some more of the bedrock concepts of nutrition science into ultra-processed eating, we’ll be able to get smarter about our ultra-processed existence and make on-the-go eating healthier.
Ultra-processed foods attack our brains
We’ve known for a long time that ultra-processed foods are associated with all kinds of bad health outcomes, from more early death, to extra strokes, and additional heart attacks.
And we know that refined carbohydrates (white bread, sugar), syrupy beverages (soda, juice), and ultra-processed meats (hot dogs) are some of the most dangerous foods in the category.
But whether the entire category — all packaged, ultra-processed foods are inherently bad for us by nature — is still an open question.
One characteristic that separates many ultra-processed foods from their unprocessed counterparts is the calorie density. Each bite of an ultra-processed meal tends to have more calories in it, without nearly as much fiber as fresh fare. That may be part of the reason ultra-processed diets can lead to overeating, Hall said: simply because each bite is rich and high-fat, yet not very satiating.
Hall’s second big hypothesis is that ultra-processed foods might drive people to eat more because they’re “hyper-palatable,” meaning they’re rich in tantalizing combinations of fat and salt, or fat and sugar, or carbohydrates and salt.
Almost nothing in nature tastes that good to us — one of the only natural “hyper-palatable” foods is a mother’s breast milk. “Breast milk can be sweet and fatty at the same time,” Hall said. We may be evolutionarily attuned to find these rarer types of composed foods irresistible, a hard-wired survival instinct.
When we cook from scratch, it’s near-impossible to include as much sodium and fat as factories do when fusing together ultra-processed foods. At home, combo dishes can still be hyper-palatable, but sugar and oils tend to bump up against watery vegetables and grains. In Hall’s landmark 2019 study, only about 40% of the foods on the unprocessed diet were hyper-palatable, while roughly 70% of the foods on the ultra-processed diet were composed of these particularly “hyper-palatable” high ratios of salt, sugar, fat, and carbohydrates.
If the easiest, cheapest, quickest dinner option involves filling your plate with mouth-wateringly delicious but low-nutrition fare, that’s exactly what you’re going to do. The question is: can we do anything to make hyper-palatable foods a little less damaging?
Change the composition of your plate
For his new experiment, Hall is trying out a few different techniques to study where the link exists between ultra-processing and weight gain.
One idea: cutting back on “hyper-palatable” foods in some ultra-processed meals. So, while the participants may still consume more calories in each bite than they would when eating an unprocessed meal, they’ll (perhaps) be less likely to overeat, since the foods won’t be as irresistible.
Another idea is to cut calories by simply adding some non-starchy vegetables to a plate of ultra-processed foods.
“You end up with more salads, for example,” he said.
If adding a side of veggies to a convenience meal ends up normalizing how many calories people eat, that could change the way we think about how we choose processed foods, and maybe even the way that manufacturers make them — if they want to change.
Can fast food ever be healthy food?
Hall has a more surgical technique he’s trying out in the experiment, too. He’s dissolving fiber supplements into some of the ultra-processed foods — stirring fiber powder into packaged yogurts, for example — to see if that curbs overeating and improves health outcomes.
This is a more straightfoward idea, and one that could be picked up by the food manufacturing industry if it shows promise.(Already, big food companies including Nestle are refomulating some packaged foods like frozen pizzas to include more fiber and protein, targeting patients on appetite-supressing GLP-1 drugs like Ozempic.)
If ultra-processed foods can actually be reformulated for health, I imagine something more idyllic than just some extra fiber sprinkled into frozen pizzas and yogurts. What about aisles of packaged goods with more beans, nuts, seeds, and less sugar in them than before? UPFs could also take a nod from traditional diets that we know work well, like Mediterranean foods rich in olive oil, lentils, chickpeas, and citrus, which are all relatively shelf-stable items that experts agree are good for your heart and your longevity. People could eat rice and beans out of a bag, or enjoy a side of vacuum-packed veggies, instead of potato chips. Those would be more health-forward choices than a “plant-based” treat like a high-fat pastry, no matter whether it is homemade or factory-built.
“All the things that we’ve known about for a long time,” are still worth taking into consideration, Hall says, no matter how processed your diet is. Seek out nuts, seeds, whole grains like oats or quinoa, black beans, hummus, lentils, and — yes — unprocessed fresh veggies and fruit when you can. Avoid sugary snacks and refined grains. These are “all the things that the dietary guidelines already discuss ad nauseam.”
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