We all know teens love snacks — but a new study suggests that ultra-processed foods may be making it harder for them to stop eating, even when they’re not hungry. According to researchers, young people who consume diets high in ultra-processed foods tend to snack more, eat extra calories, and possibly gain weight over time.
This new research highlights how certain foods may not just be unhealthy — they may actually change how young people think about hunger and respond to food.
What Are Ultra-Processed Foods?
Ultra-processed foods (UPFs) are items that go far beyond simple cooking. They’re often made from extracts and additives rather than whole food ingredients. These include:
- Packaged snacks and baked goods
- Sugary cereals
- Instant noodles and frozen meals
- Deli meats and processed cheeses
They often contain:
- Saturated fats
- Added sugars
- Refined starches
- Artificial flavours, colours, and preservatives
According to the researchers, people aged 15 to 24 in the U.S. currently get up to 65% of their daily calories from ultra-processed foods.
The Study: How UPFs Affected Young Adults’ Eating Habits
The study, published on November 19, 2025, in the journal Obesity, involved 27 participants aged 18 to 25. Each participant followed one of two special diets for two weeks:
- One diet had 81% of calories from ultra-processed foods.
- The other diet had no ultra-processed foods at all.
The two diets were carefully designed to match in nutrients like:
- Macronutrients (carbs, fats, proteins)
- Added sugars
- Vitamins and minerals
- Fiber and energy density
This ensured that any changes in eating behavior could be linked more directly to how the food was processed, not what nutrients it contained.
What Happened After the Diets Ended?
After the two-week diet phase, researchers observed the participants for a month of “normal” eating. They tracked how much food the young adults consumed, especially during:
- A buffet-style breakfast
- Snacking opportunities afterward
The Results:
- Younger participants (ages 18–21) who had been on the ultra-processed food diet ate more calories at breakfast.
- They also snacked more after breakfast, even when they weren’t hungry.
- This snacking without hunger was not observed in those who had eaten a diet of unprocessed or minimally processed foods.
These findings suggest that exposure to ultra-processed food may increase the tendency to overeat, particularly in late teens and young adults.
Why This Matters for Teen Health
According to Dr. Brenda Davy, senior author of the study, while the trial was short-term, the impact could be long-lasting if overeating continues. She warned that consistent excess calorie intake could lead to weight gain and related health issues such as:
- Obesity
- Metabolic syndrome
- Poor heart health
Dr. Alex DiFeliceantonio, another researcher, noted that snacking when not hungry is a strong early sign of future weight gain in adolescents.
What’s Next in This Research?
The research team believes further studies are needed, especially among:
- Younger teens (under 18)
- Larger and more diverse groups
- “Real-world” settings outside labs or clinics
They also want to explore how ultra-processed foods affect brain activity, hormones, and biomarkers that control hunger, fullness, and pleasure from eating.
What Can Parents and Teens Do?
While more research is underway, experts already recommend:
- Limiting ultra-processed foods at home
- Encouraging whole foods like fruits, vegetables, whole grains, and lean proteins
- Teaching mindful eating — eating when hungry, stopping when full
Simple switches, like swapping chips for nuts or soda for water, can go a long way in building healthier eating habits.
