Researchers wanted to understand why ultra-processed foods lead people to eat more calories. They tested whether the texture of food—which affects how quickly you eat—makes a difference. For two weeks, 41 people ate either soft, easy-to-eat ultra-processed foods (which they ate quickly) or chewier ultra-processed foods (which took longer to eat). People eating the slower foods consumed about 370 fewer calories per day without trying to diet. This suggests that how fast we eat, determined by food texture, plays a real role in controlling how much we eat.

The Quick Take

  • What they studied: Does eating speed (controlled by food texture) affect how many calories people eat when eating ultra-processed foods?
  • Who participated: 41 healthy adults (average age 27, average weight 154 pounds) with normal body weight participated in the study
  • Key finding: When eating slower-textured ultra-processed foods, people ate about 370 fewer calories per day compared to eating fast-textured ultra-processed foods, even though both diets tasted equally good and had the same amount of food available
  • What it means for you: If you eat ultra-processed foods, choosing foods that require more chewing might help you eat less without feeling deprived. However, this study only lasted two weeks, so we don’t know if this effect continues long-term or helps with weight loss over months

The Research Details

This was a carefully controlled experiment where the same 41 people ate two different diets for two weeks each, with a two-week break between them. The researchers created two versions of ultra-processed foods: one with soft, easy-to-eat textures (like soft bread and smooth foods) and one with chewier, harder-to-eat textures (like foods requiring more chewing). The participants didn’t know which diet was which (called “single-blind”), and the researchers made sure both diets tasted equally good, had the same portion sizes offered, and included the same variety of foods. The only real difference was how fast people naturally ate each diet.

Participants could eat as much as they wanted from either diet (called “ad libitum”), and researchers carefully measured everything they ate. They also measured body weight and body fat before and after each diet period. This type of study design is very strong because each person serves as their own comparison—we can see how the same person’s eating changes between the two diets.

Understanding why ultra-processed foods lead to overeating is important for public health. If we can identify specific features of these foods (like texture) that cause people to eat more, we might be able to design better food policies or help people make smarter food choices. This study goes beyond just observing that people eat more of these foods—it actually tests whether changing one specific feature (eating speed) causes a change in how much people eat.

This study has several strengths: it was a randomized controlled trial (the gold standard for testing cause-and-effect), it controlled for many variables that could affect results (taste, portion size, food variety), and it used objective measurements of food intake. The study was published in a highly respected nutrition journal. However, the sample size was relatively small (41 people), and all participants were young, healthy adults with normal weight, so results might not apply to older people, people with obesity, or those with different health conditions. The study only lasted two weeks, so we don’t know if these effects continue over months or years.

What the Results Show

The main finding was clear and statistically significant: people eating the slow-eating-rate ultra-processed foods consumed an average of 369 fewer calories per day compared to when they ate the fast-eating-rate ultra-processed foods. This difference was consistent throughout the two-week period, meaning it wasn’t just a first-day effect—it sustained the entire time. To put this in perspective, 369 calories per day equals about 2,583 calories over a week, which is roughly equivalent to one pound of body weight.

Interestingly, even though people ate fewer calories on the slow-eating diet, their total body weight didn’t change significantly in either diet period. However, the researchers did find that body fat decreased by about one pound (0.43 kg) on the slow-eating diet. This suggests that the slower eating may have led to some beneficial changes in body composition, even if the scale didn’t show major weight loss.

The study also confirmed that the two diets truly differed in eating speed—people naturally ate the soft foods much faster than the chewy foods, which was the whole point of the experiment. This validates that the researchers successfully created the conditions they intended to test.

The study found that body fat mass specifically decreased on the slow-eating diet, even though total body weight remained relatively stable. This is important because it suggests the body may have been using stored fat for energy rather than just losing water weight. The researchers also confirmed that palatability (how good the food tasted) didn’t differ between the two diets, which is crucial because it means people weren’t eating less of the slow-eating diet simply because they liked it less.

Previous research has shown that people eat more calories from ultra-processed foods compared to whole foods, and that eating speed affects how much people eat in general. This study builds on that knowledge by showing that even within ultra-processed foods, the texture (which determines eating speed) significantly affects calorie intake. The finding supports the theory that our bodies use sensory cues—like how long we spend chewing—to help regulate how much we eat. This aligns with research showing that slower eating gives our brain more time to register fullness signals.

The study only lasted two weeks, so we don’t know if people would continue eating fewer calories if they stuck with slow-eating foods for months or years. The participants were all young (average age 27), healthy, and had normal body weight, so results might be different for older adults, people with obesity, or those with certain health conditions. The study used only ultra-processed foods, so we don’t know if eating speed affects calorie intake from whole foods the same way. Additionally, the study was conducted in a controlled setting where food was provided, which is different from real-world eating where people choose their own foods. Finally, the sample size of 41 people is relatively small, so larger studies would help confirm these findings.

The Bottom Line

If you regularly eat ultra-processed foods, choosing versions that require more chewing (like whole grain crackers instead of soft white bread, or firmer textures instead of soft ones) may help you eat fewer calories without feeling like you’re restricting yourself. This is a low-risk strategy worth trying. However, the strongest recommendation would be to reduce ultra-processed foods overall and eat more whole foods like fruits, vegetables, and whole grains, which naturally require more chewing and are more nutritious. Confidence level: Moderate for short-term effects (this study shows it works for two weeks), but low for long-term effects (we need longer studies).

This research is most relevant for people who eat a lot of ultra-processed foods and want to reduce their calorie intake without strict dieting. It may be particularly helpful for people who struggle with portion control or who feel hungry when they try to eat less. However, if you already eat mostly whole foods or if you have certain eating disorders, this research may not directly apply to you. People with swallowing difficulties or dental problems should consult their doctor before making major changes to food texture.

Based on this study, you could expect to see changes in calorie intake within days to a week of switching to slower-eating-rate foods. However, changes in body weight typically take several weeks to become noticeable (usually 3-4 weeks minimum). The study only measured effects over two weeks, so we don’t know what happens after that timeframe.

Want to Apply This Research?

  • Track the texture of ultra-processed foods you eat (soft vs. chewy) and note your total calorie intake for each day. Over 1-2 weeks, compare your average daily calories on days when you eat mostly soft ultra-processed foods versus days when you eat chewier versions. This will show you personally whether eating speed affects your intake.
  • When shopping for ultra-processed foods, deliberately choose versions with firmer or chewier textures. For example: select whole grain bread instead of white bread, choose firm crackers instead of soft ones, pick chewy granola bars instead of soft ones. Set a goal to make this swap for one meal per day for one week and track how it affects your hunger and calorie intake.
  • Weekly, record which ultra-processed foods you ate and their texture (soft/medium/chewy). Track your average daily calorie intake for weeks when you primarily eat soft textures versus weeks when you eat chewier textures. Also monitor how full you feel after meals and whether you snack less between meals. This long-term tracking will help you understand if this strategy works for your individual eating patterns.

This research suggests that food texture may affect how much ultra-processed food people eat, but it is not medical advice. This study lasted only two weeks and involved young, healthy adults, so results may not apply to everyone. Before making significant changes to your diet, especially if you have a medical condition, take medications that affect appetite, or have a history of eating disorders, consult with your doctor or registered dietitian. This study does not replace professional medical or nutritional guidance, and individual results may vary.