Scientists have finally proven that ultra-processed junk food causes weight gain - not just raises risks it - according to a new National Institutes of Health (NIH) study.
We've known for decades that people whose diets involve a lot of soda, candy, pizza and chips are more likely to overeat and become overweight.
But despite its small size - consisting of just 20 people - the new study claims to have shown that these foods cause consumers to eat too much and gain weight, while healthier whole foods cause people to shed pounds.
The researchers said they aren't yet sure what it is about processed food that causes over eating and weight gain, but because the two diets they put participants were matched for dietary content, it's clear the key is in processing itself.
When volunteers ate meals like this one, consisting of quesadillas, refried beans, and diet lemonade, the ultra-processed foods caused them to overeat and gain weight in a new study
Lawmakers in some states have tried to ban ultra-processed foods, documentaries have tried to expose their empty calories, and countless studies have linked them to obesity, diabetes, poorer heart health and shorter lifespans.
Ultra-processed foods have long been a prime target of the battle against the obesity epidemic.
But they've never before been proven to actually cause weight gain in and of themselves.
To establish this ground-breaking finding, the National Institute on Diabetes and Digestive and Kidney Diseases (NIDDK) put 10 healthy adult men and 10 health adult women volunteers on tightly controlled diets for a month.
Each volunteer was randomly assigned to one of two meal plans - highly-processed or unprocessed - for two weeks and then switched to the other plan.
A processed breakfast might be a bowl of Honey Nut Cheerios doused in fiber-enriched milk, with the kind of sweating packaged blueberry muffin you might see in a vending machine and some margarine to spread on it.
By contrast, on the unprocessed diet, a volunteer might be served a plain Greek yogurt-based parfait with strawberries, bananas, walnuts salt and olive oil and some apple slices drizzled in fresh squeezed lemon.
Crucially, the scientists made sure that each meal had the same amounts of the same nutritional components - including fat, carbohydrates and protein - and allowed the participants to eat as much of each meal as they wanted.
The primary difference in the makeup of the two meals was that sugar and fat had to be added to the processed meals, while it occurred naturally in the unprocessed ones.
NIH researchers served participants entirely unprocessed meals like this one of chicken salad, blueberries almonds and milk. They had the same nutritional values as the processed meals, yet study
