Research from the University of Bristol has revealed that adhering to a wholefood diet allows individuals to consume significantly larger quantities of food while still reducing their caloric intake. The study indicates that those who choose unprocessed foods tend to eat over 50% more than those consuming ultra-processed foods (UPFs), yet consume on average **330 fewer calories** daily. Published in *The American Journal of Clinical Nutrition* on **March 15, 2024**, these findings offer new insights into dietary choices and suggest that humans possess an innate ability to prioritize nutrition when consuming foods in their natural form.
According to lead author Jeff Brunstrom, a Professor of Experimental Psychology at the University of Bristol, when presented with unprocessed options, individuals instinctively select foods that balance enjoyment, nutrition, and satiety. Brunstrom highlighted the importance of this research, stating, “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 researchers reanalysed data from a notable clinical trial led by veteran scientist Dr. Kevin Hall from the US National Institutes of Health. This trial initially demonstrated that a diet consisting exclusively of UPFs leads to excessive calorie consumption and subsequent weight gain. However, the new analysis presents a more complex picture, showing that participants on a wholefood diet opted for higher volumes of fruits and vegetables, often consuming several hundred grams per meal, rather than calorie-dense options like meat, pasta, or cream.
The dramatic increase in food intake among those on the unprocessed diet resulted in a **57% increase by weight** compared to those consuming UPFs. The research team evaluated the nutritional quality of the participants’ diets, revealing that the diverse array of fruits and vegetables provided essential vitamins and minerals. These nutrients would likely be lacking if participants had chosen only higher-calorie wholefoods.
Co-author Mark Schatzker, an acclaimed food writer, noted that consuming only calorie-rich foods would have led to deficiencies in several essential vitamins and minerals. He stated, “Those micronutrient gaps were filled by lower-calorie fruits and vegetables,” emphasizing the critical role of nutrient-rich foods in maintaining dietary balance.
The study introduces the concept of “micronutrient deleveraging,” which suggests that individuals naturally prioritize foods rich in micronutrients, such as fruits and vegetables, over energy-dense alternatives. This phenomenon contrasts sharply with the narrative surrounding UPFs, which are often considered to provide “empty calories.” The research indicates that these processed foods can actually meet micronutrient requirements, frequently through fortification. For instance, calorie-rich options like French toast sticks and pancakes provide significant amounts of vitamin A, while wholefoods like carrots and spinach, which are lower in calories, also deliver this essential nutrient.
Senior Research Associate Dr. Annika Flynn from the University of Bristol raised concerns about the implications of these findings. She stated, “This raises the alarming possibility that UPFs deliver both high energy and micronutrients in one hit, which could result in calorie overload.” This overload can diminish the beneficial interplay between calorie content and nutrient density.
Further analysis of UPFs reveals that they may lead consumers toward higher-calorie choices, which, even in smaller quantities, can contribute to excess energy intake and fuel obesity. Professor Brunstrom emphasized that overeating is not necessarily the primary issue. He noted, “Our research clearly demonstrated consumers on a wholefood diet actually ate far more than those on a processed food one.”
Additionally, recent studies from the University of Bristol indicate that altering the presentation of healthier, more environmentally-friendly dishes in menus can prompt diners to make better choices. This suggests that promoting “healthy competition” among food options can encourage consumers to opt for more nutritious meals.
The research was supported by the National Institute for Health and Care Research (NIHR) Bristol Biomedical Research Centre, further reinforcing the need for ongoing exploration of dietary impacts on health and behaviour.
For further information or to request interviews with lead author Professor Jeff Brunstrom or co-author Mark Schatzker, please contact Victoria Tagg, News & Content Manager (Research), University of Bristol at [email protected]. The study will be accessible online following the release of the embargo.
