Individuals who adopt an unprocessed food diet as part of their New Year’s resolutions might discover that this dietary adjustment influences their eating habits in an unexpected manner. Rather than opting for calorie-heavy whole foods like rice, meat, or butter, they instinctively gravitate toward consuming substantially larger portions of fruits and vegetables. This natural shift in preferences can facilitate weight loss without the need for conscious calorie counting or portion control.
A comprehensive study conducted by scientists at the University of Bristol, in collaboration with prominent nutrition specialists from the United States, revealed that participants restricted to unprocessed foods ingested over 50 percent more food by weight compared to those limited to ultra-processed foods (UPFs). Remarkably, despite this increased volume, their average daily calorie consumption dropped by approximately 330 calories.
A Natural Mechanism for Balancing Nutrition and Energy Intake
These findings, published in The American Journal of Clinical Nutrition, shed new light on the decision-making processes behind human food selection. The evidence bolsters the concept of an innate “nutritional intelligence” in humans that promotes balanced dietary choices. This inherent mechanism seems to operate most effectively with foods in their natural, unadulterated state, potentially undermined by the prevalence of contemporary fast food options.
Jeff Brunstrom, the lead author and Professor of Experimental Psychology at the University of Bristol, commented: “It’s fascinating to observe that when presented with unprocessed alternatives, individuals intuitively choose foods that harmonize pleasure, nutritional value, and satiety, all while lowering total energy consumption. Our food selections are far from arbitrary; in reality, we demonstrate remarkably astute judgment when encountering foods in their unaltered form.”
Revisiting a Pivotal Trial on Processed Foods
This investigation represents a novel reexamination of data from a groundbreaking clinical trial spearheaded by Dr. Kevin Hall, a seasoned researcher at the US National Institutes of Health. The initial trial demonstrated that diets consisting solely of ultra-processed foods prompted excessive eating and subsequent weight gain. The current analysis delves deeper into the reasons why participants on unprocessed diets opted for significantly larger servings of specific foods yet achieved lower overall calorie intake.
Those following the unprocessed regimen consistently incorporated generous amounts of fruits and vegetables into their meals, often consuming hundreds of grams per sitting. They showed a clear preference away from energy-dense items such as steak, pasta, and cream. Consequently, the whole-food group ate 57 percent more food by weight than their counterparts.
Fruits and Vegetables Bridge Essential Nutrient Deficiencies
The researchers also assessed the nutritional quality of these diets. They determined that the diverse and abundant intake of fruits and vegetables supplied critical vitamins and minerals that would otherwise be absent if diets relied predominantly on higher-calorie whole foods.
Mark Schatzker, a co-author and writer of The Dorito Effect and The End of Craving, elaborated: “If the participants had limited themselves to only the calorie-dense foods, the results indicated deficiencies in key vitamins and minerals, potentially leading to micronutrient shortfalls over time. These gaps were effectively addressed by incorporating low-calorie fruits and vegetables.”
The team attributes this pattern to what they term “micronutrient deleveraging.” Essentially, this suggests that people naturally favor vitamin- and mineral-rich foods like fruits and vegetables, even at the expense of reducing intake of more calorically potent alternatives.
The Disruptive Impact of Ultra-Processed Foods
In stark contrast, ultra-processed foods yielded entirely different results. Although frequently criticized for delivering “empty calories,” the study indicates they can fulfill micronutrient requirements, primarily due to added fortifications. For instance, high-calorie items like French toast sticks and pancakes emerged as significant providers of vitamin A. On the unprocessed diet, this vitamin was chiefly sourced from low-calorie options such as carrots and spinach.
Dr. Annika Flynn, a Senior Research Associate at the University of Bristol and co-author, noted: “This discovery highlights a concerning aspect: UPFs may supply both excessive energy and micronutrients simultaneously, potentially causing calorie surplus by eliminating the advantageous exchange between caloric content and nutrient density.”
She further explained that whole foods reinstate this equilibrium by fostering a competitive dynamic between nutrient-packed, lower-calorie choices and higher-energy ones, thereby guiding individuals toward fruits and vegetables over staples like pasta and meat.
How Processed Foods Alter Contemporary Eating Patterns
These insights provide deeper understanding of how the pervasive intake of highly processed foods might shape eating behaviors and choices. The researchers argue that overeating may not be the primary issue at hand.
Professor Brunstrom emphasized: “Overeating isn’t inherently the fundamental challenge. Our study unequivocally showed that those on a whole-food diet consumed considerably more food than those on processed diets. However, the composition of the food itself directs selections, with UPFs subtly pushing toward calorie-intensive picks. Even in smaller amounts, these contribute to surplus energy consumption, thereby promoting obesity.”
Minor Adjustments for Promoting Better Dietary Decisions
Additional research from the University of Bristol demonstrates that subtle modifications can significantly sway choices. In one related experiment, merely reordering healthier, more sustainable meal options on a weekly menu increased their selection rates among diners.
The study received funding from the National Institute for Health and Care Research (NIHR) Bristol Biomedical Research Centre (Bristol BRC).
