Do Ultra-Processed Foods Cause Weight Gain? A New Study Says Chewing Might Be the Key

How Ultra-Processed Foods Contribute to Weight Gain — And What Chewing Has to Do With It A nutrition insight from a physical therapist’s perspective If you've ever wondered why some foods seem to make you hungrier rather than satisfied, you're not alone. A fascinating study published in Diabetes, Obesity & Metabolism shed new light on how ultra-processed foods contribute to weight gain — and surprisingly, one of the key culprits might be how little we chew them.

What Are Ultra-Processed Foods?

Ultra-processed foods are those that have been heavily modified from their original form. Think packaged snacks, frozen meals, fast food, sugary drinks, and even many protein bars and cereals. These products often contain additives, preservatives, emulsifiers, and flavor enhancers that make them shelf-stable and hyper-palatable.

The Study: Real Food vs. Ultra-Processed

Researchers at the NIH conducted a randomized, controlled crossover study where participants spent two weeks eating a diet composed mostly of ultra-processed foods and another two weeks eating minimally processed foods. Importantly, meals were matched for calories, sugar, fat, fiber, and macronutrients — so the only real difference was how processed the food was.

The result? On the ultra-processed diet, participants consumed about 500 more calories per day and gained an average of 2 pounds in just two weeks. When they switched to the unprocessed diet, they lost weight.

The Chewing Connection

One of the most interesting findings was that people chewed significantly less when eating ultra-processed foods. Less chewing often means faster eating — and faster eating has been linked in many studies to reduced satiety and increased calorie intake. In other words, you’re more likely to overeat when your food is soft, pre-chewed by machines, or designed to go down quickly.

As a physical therapist who often talks about lifestyle and wellness with patients, I find this especially relevant. Many people don’t realize that how you eat is just as important as what you eat.

Why This Matters for Your Health

Chronic overconsumption of ultra-processed foods has been linked not only to weight gain but also to inflammation, metabolic dysfunction, and reduced gut health. And for patients recovering from injury or dealing with chronic pain, carrying excess weight or fueling with inflammatory foods can slow healing and worsen outcomes. Here are a few simple tips to shift toward a healthier, more mindful approach:

Choose whole foods: Fruits, vegetables, lean meats, legumes, and grains in their natural form.
Slow down: Chew thoroughly and savor your meals. Try putting your fork down between bites and chewing mindfully.
Look at labels: The longer the ingredient list the more processed it likely is.
Batch cook at home: It’s one of the best ways to control ingredients and avoid hidden additives.

Ultra-processed foods aren't just sneaky in terms of ingredients — they may be causing you to eat more by reducing how much you chew and how full you feel. By paying attention to food texture, cooking more at home, and slowing down your meals, you can better support your health, longevity, and even your recovery if you’re working through injury.