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| source : theguardian.com |
When Guillaume Raineri moved from a small town near Paris to suburban Maryland, he expected a few cultural adjustments, maybe new customs, new slang, and definitely new weather. But what caught him completely off guard? The food.
“I couldn’t believe the portion sizes,” he said. “And everything was… sweeter. Even the bread.”
That curiosity, and a dash of concern, led him to volunteer for a study at the National Institutes of Health (NIH). What followed was a deeply controlled (and revealing) look into why the American diet is making so many of us sick, and what food processing might have to do with it.
I Went Down a Rabbit Hole, and So Did He
I’ve been reading more about ultra-processed foods lately, those boxed, bagged, and seemingly harmless snacks we all grew up with, and it turns out, they’re not just empty calories. They might be a key driver behind America’s soaring rates of obesity, diabetes, and heart disease.
Raineri, a former HVAC tech, became a human guinea pig in the NIH’s metabolic ward, a highly controlled research facility where every bite he took was tracked. For one week, he ate a diet full of whole foods: grilled chicken, fresh veggies, nothing too flashy.
He felt great.
Then came the “American” week: frozen meals, chicken nuggets, sugary cereal, peanut-butter-and-jelly sandwiches. All the familiar, ultra-processed staples of the U.S. diet.
“It just sat in my stomach,” he said. “I felt bloated and irritable.”
And scientifically? The results were shocking. Raineri, and others in the study, ate about 500 extra calories per day when on the ultra-processed diet. They gained weight, their insulin spiked, and their blood sugar climbed.
Wait, Is It Really Processing That’s the Problem?
Yes. According to Kevin Hall, the NIH scientist leading the study (and former physicist-turned-nutrition-researcher), it's not just the salt, sugar, or fat that's hurting us, it's how our food is made.
This isn’t just about junk food or fast food. It’s about the hidden ingredients in what looks like healthy food.
Ultra-processed foods, a term first coined by Brazilian researcher Carlos Monteiro, are products that have been so altered from their natural form they’re practically unrecognizable. Think artificial flavors, emulsifiers, gums, preservatives, and stuff you’d never find in your kitchen.
These foods are engineered to be hyper-palatable, so tasty they override your natural fullness cues. You don’t just eat a handful of chips. You eat the bag.
Your Gut (Literally) Can’t Digest This Lifestyle
One of the most eye-opening things I learned while digging into this topic? Your gut bacteria are suffering.
NIH researchers found that people eating ultra-processed diets had less microbial diversity in their gut, and some of the "good" bacteria literally started feeding on the gut’s protective mucus lining, which can lead to inflammation.
And if you think switching to “no sugar added” processed snacks helps, think again. Artificial sweeteners mess with your microbiome too, impairing your body’s ability to regulate blood sugar.
What About Factory-Made “Healthy” Foods?
This isn’t black-and-white.
Not all processed foods are evil. Take Seviroli Foods, a pasta manufacturer in New York. Their products are processed, but they avoid hydrogenated oils and limit additives. Even so, they still fall into the “ultra-processed” category.
NYU professor Marion Nestle, a respected voice in nutrition, points out the gray areas: A loaf of whole wheat bread might look healthy but could be ultra-processed depending on the ingredients. Same with “light” yogurt that's full of stabilizers and thickeners.
It’s not just what you eat, it’s how it was made.
So, What Can We Actually Do?
First, don’t panic. I’m not suggesting you throw out every packaged food in your kitchen. But the research is clear: the less ultra-processed food in your life, the better.
Here are a few practical tips I’ve picked up from experts:
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Prioritize fiber. Your gut bacteria love it. Think beans, lentils, veggies, and fruits, especially berries.
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Cook at home more often. You control the ingredients.
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Read labels. If the ingredients list reads like a chemistry textbook, it’s probably ultra-processed.
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Don’t demonize fat or carbs, it’s the combo of ultra-processing and hyper-palatable flavors that causes the biggest damage.
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Think whole food first. Aim for ingredients you recognize: olive oil, oats, eggs, real meat, real vegetables.
The Bottom Line
America’s food landscape has evolved into something hyper-industrial and disturbingly addictive. And while nutrition debates rage on, from keto to vegan to intermittent fasting, one thing’s becoming crystal clear:
Ultra-processed food is quietly killing us.
It’s not about fear-mongering. It’s about being informed and intentional.
As Kevin Hall put it, “We’re starting to learn that processing really matters.”
So the next time you’re standing in the snack aisle, just ask: Could I make this in my kitchen? If the answer is “definitely not,” maybe put it back.