For many people, the start of a new year brings promises to eat better and improve health.
One popular resolution is to cut back on highly processed foods and focus instead on foods that are closer to their natural form.
While some worry that eating only unprocessed foods might mean feeling hungry or struggling to control portions, new research suggests the opposite may be true.
In fact, choosing real, unprocessed foods may naturally guide people toward healthier eating patterns without the need to count calories or restrict portions.
A study led by researchers at the University of Bristol, working with nutrition experts from the United States, examined how people behave when they eat only unprocessed foods compared with diets made entirely of ultra-processed foods.
Ultra-processed foods are products that have been heavily altered during manufacturing and often include additives, refined ingredients, and artificial flavors. Examples include packaged snacks, sugary cereals, frozen meals, and many fast foods.
Unprocessed foods, on the other hand, include fruits, vegetables, whole grains, fresh meat, and foods that closely resemble their natural state.
The researchers found something surprising. People who ate only unprocessed foods actually ate much more food by weight. On average, they consumed more than 50 percent more food than people who ate only ultra-processed foods.
Despite this larger volume of food, their daily calorie intake was about 330 calories lower. This means they ate more food overall but still consumed fewer calories.
The study, published in The American Journal of Clinical Nutrition, helps explain how people make food choices when given different types of food. According to the researchers, humans may have a natural ability to balance nutrition and energy intake.
This built-in guidance seems to work best when food is eaten in its natural form. When food becomes heavily processed, this internal system may be disrupted.
Professor Jeff Brunstrom from the University of Bristol, the lead author of the study, explained that when people are offered unprocessed foods, they tend to choose meals that feel enjoyable, filling, and nutritious at the same time.
Rather than randomly selecting foods, people appear to make sensible decisions that help meet their body’s needs. This challenges the idea that people always lack control around food or make poor choices when left to their own instincts.
To better understand why this happens, the researchers reexamined data from a well-known clinical trial led by Dr. Kevin Hall at the U.S. National Institutes of Health.
That original study showed that people who ate only ultra-processed foods tended to overeat and gain weight. The new analysis focused on what people actually chose to eat when they were restricted to whole foods.
The results showed that participants eating unprocessed foods naturally filled their plates with fruits and vegetables. They often ate several hundred grams of these foods at a time. At the same time, they tended to eat less of higher calorie foods such as pasta, steak, butter, and cream.
Because fruits and vegetables are low in calories but high in volume, people could eat large amounts and still feel full while consuming fewer calories overall.
The researchers also looked at the nutritional quality of the diets. They found that fruits and vegetables played an important role in providing essential vitamins and minerals.
If participants had focused only on calorie-rich whole foods, they would have missed out on key nutrients and eventually developed vitamin and mineral shortages. Lower calorie foods like vegetables helped fill these gaps.
One of the study’s co-authors, Mark Schatzker, explained that this behavior suggests people naturally seek out foods rich in vitamins and minerals.
When those nutrients are missing, people may continue eating until the body’s needs are met. This process, described as prioritizing micronutrients, appears to push people toward fruits and vegetables when they eat whole foods.
Ultra-processed foods change this balance in a troubling way. Although they are often described as “empty calories,” many are fortified with vitamins and minerals. This means they can deliver both high energy and nutrients at the same time.
For example, some processed breakfast foods turned out to be major sources of vitamin A, even though they are high in calories. In contrast, whole-food sources of vitamin A, such as carrots and leafy greens, provide far fewer calories.
Dr. Annika Flynn from the University of Bristol warned that this combination may encourage overeating.
When high-calorie foods also meet nutrient needs, people may consume more energy than their bodies require. Whole foods restore a healthier balance by creating a trade-off between calories and nutrients, gently pushing people toward lower calorie, nutrient-rich foods.
When reviewing and analyzing the study’s findings, the main message is clear. The problem with modern diets may not be overeating itself, but the types of foods people are eating.
Those on whole-food diets actually ate more, yet consumed fewer calories and likely felt more satisfied. Ultra-processed foods appear to guide people toward energy-dense choices that are easy to overconsume.
The findings suggest that small changes, such as choosing less processed foods or adjusting how options are presented, can have a powerful influence on eating behavior. Rather than relying on strict rules or willpower, improving the food environment may help people make healthier choices naturally.
This research adds strong support to the idea that eating real food allows the body’s natural instincts to work as intended, promoting better nutrition, healthier weight, and long-term well-being.
If you care about nutrition, please read studies about the power of beetroot juice, and the risks of mixing medications with dietary supplements.
For more health information, please see recent studies about how to boost iron intake: natural solutions for anemia, and results showing vitamin K may lower your heart disease risk by a third.
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