Whole Foods Diet Helps People Eat More And Lose Weight

For decades, the debate over what really makes a healthy diet has raged on, with ultra-processed foods (UPFs) often cast as the villain in a world awash with fast food and convenience meals. But a groundbreaking new study, published on January 21, 2026, in The American Journal of Clinical Nutrition, has delivered some of the clearest evidence yet that the answer may lie in the most obvious place: eating more food in its most natural, unprocessed form.

The research, led by Professor Jeff Brunstrom of the University of Bristol and co-authored by top US nutritional experts, re-examined data from a pivotal 2019 clinical trial. The original trial, led by Dr. Kevin Hall of the US National Institutes of Health, had already shown that eating a diet rich in ultra-processed foods led to excessive calorie intake and weight gain. But this new analysis dug deeper, revealing a surprising twist: people who switched to an entirely unprocessed, whole foods diet ate a whopping 57% more food by weight than those consuming UPFs—yet, astonishingly, they still took in an average of 330 fewer calories per day.

"It's exciting to see when people are offered unprocessed options they intuitively select foods that balance enjoyment, nutrition, and a sense of fullness, while still reducing overall energy intake," Brunstrom told The Independent. "Our dietary choices aren't random—in fact, we seem to make much smarter decisions than previously assumed when foods are presented in their natural state."

The study’s findings, echoed across outlets from LIGA.net to Medical Xpress, suggest that the body possesses an innate "nutritional intelligence"—a kind of internal compass that guides us toward foods rich in essential vitamins and minerals, especially when we’re presented with whole, unprocessed options. This nutritional intelligence, as the researchers describe it, appears to be impaired by today's fast food culture and the overwhelming presence of UPFs in modern diets.

So, what exactly did the participants eat? Those on the whole foods diet consistently loaded up on fruits and vegetables, sometimes consuming several hundreds of grams per meal. Instead of gravitating toward calorie-dense choices like steak, pasta, or cream, they naturally opted for lower-calorie, nutrient-packed produce. This behavior, the study found, wasn't just about eating more food by weight—it was about eating smarter.

"Had participants eaten only the calorie-rich foods, our findings showed they would have fallen short on several essential vitamins and minerals and eventually developed micronutrient insufficiencies. Those micronutrient gaps were filled by lower-calorie fruits and vegetables," explained co-author Mark Schatzker, author of The Dorito Effect and The End of Craving, in comments reported by Medical Xpress.

The implications are striking. While participants on the whole foods diet ate more by weight, they achieved a better balance of enjoyment, nutrition, and satiety—leading to a reduction in overall calorie consumption. In contrast, those consuming ultra-processed foods not only took in 508 more calories daily (leading to an average two-pound weight gain in just a week, according to Jang), but also risked missing out on the crucial micronutrients found in fruits and vegetables unless those nutrients were artificially added through fortification.

This vitamin fortification, the researchers found, is a double-edged sword. While UPFs can deliver necessary micronutrients—sometimes even more than their unprocessed counterparts—they often do so alongside a hefty dose of calories. For instance, the foods richest in vitamin A in the UPF group were calorie-dense items like French toast sticks and pancakes. Meanwhile, those on the whole foods diet got their vitamin A from carrots and spinach, which are much lower in calories.

Dr. Annika Flynn, a senior research associate at the University of Bristol and co-author of the study, highlighted the risks: "This raises the alarming possibility that UPFs deliver both high energy and micronutrients in one hit, which could result in calorie overload, because they effectively kill the beneficial trade-off between calories and micronutrients. Conversely, this healthy competition is promoted by whole foods and therefore encourages people eating them to favour micronutrient powerhouses, such as fruit and veggies, over high-energy options like pasta and meat."

The researchers coined the term "micronutrient deleveraging" to describe this phenomenon, where humans—when given the choice—prioritize micronutrient-rich foods at the expense of energy-dense options. This, they argue, is a key mechanism by which whole foods diets help people naturally limit their calorie intake and avoid the pitfalls of obesity.

Professor Brunstrom elaborated further in Nation.Cymru: "Overeating is not necessarily the core problem. Indeed, our research clearly demonstrated consumers on a whole-food diet actually ate far more than those on a processed food one. But the nutritional make-up of food is influencing choices and it seems that UPFs are nudging people towards higher calorie options, which even in much lower quantities, are likely to result in excess energy intake and, in turn, fuel obesity."

These findings challenge the long-held assumption that simply eating less is the key to weight loss. Instead, the type of food consumed—and the body’s natural inclination to seek out nutrients when given wholesome choices—may be far more important. The study’s re-analysis showed that when participants were offered only unprocessed foods, their bodies seemed to "know" to select more fruits and vegetables, balancing out their nutritional needs while naturally curbing calorie intake.

Experts say this research could have profound implications for public health, especially as ultra-processed foods continue to dominate supermarket shelves and restaurant menus worldwide. The notion that eating more food—if it’s the right kind—can actually help people lose weight and avoid nutrient deficiencies turns conventional dieting wisdom on its head.

Of course, the study’s authors caution that simply switching to a whole foods diet isn’t a magic bullet. But the evidence is clear: when people are given the opportunity to eat unprocessed foods, their bodies make remarkably smart choices, favoring nutrition and fullness over empty calories. And as fast food culture continues to grow, understanding and harnessing this innate nutritional intelligence may be more important than ever.

The research, as published in The American Journal of Clinical Nutrition, offers a hopeful message: eating well doesn’t have to mean eating less. Sometimes, it’s just about eating better—and letting our bodies do the rest.