You have likely heard by now that ultra-processed foods sit near the very top of the list of things you can consume that are detrimental to your health and overall body composition. Observational studies have repeatedly linked a high intake of ultra-processed foods with a litany of negative health outcomes, ranging from unwanted weight gain and metabolic complications to a higher overall risk of mortality. At the same time, you have likely heard the increasingly popular counter-perspective in modern nutritional science: that there are not inherently any strictly "good" or "bad" foods, and that as long as you manage your daily energy intake, hit your recommended fiber targets, and do your best to consume mostly whole foods, the occasional or even moderate inclusion of some ultra-processed foods is likely not a major issue from a broader health perspective.
This perennial debate leaves a compelling scientific question on the table. What would happen if a person were to consume an exclusive or near-exclusive diet of ultra-processed foods while still meticulously adhering to general, established nutrition guidelines? And how would the physical and metabolic outcomes of that diet directly compare to a minimally processed diet that adheres to those exact same nutritional guidelines?
A new randomized crossover study published in scientific literature examined that exact question. The clinical trial included 55 adult participants who were classified as either overweight or obese, having them follow either an ultra-processed or a minimally processed diet over a prolonged period. The particularly notable aspect of this study’s design was the breadth of assessments administered to the participants, providing researchers with a nuanced, multi-faceted understanding of how both dietary approaches impacted their physiological systems. These evaluations tracked changes in body composition through bioelectrical impedance analysis, alongside fasting biomarkers, resting heart rate, blood pressure, and several other health parameters.
The study utilized a rigorous crossover architecture. Participants were first randomized to either the ultra-processed diet or the minimally processed diet, following their assigned nutritional protocol for a duration of eight weeks. During this period, they were retested at the midway point and again at the final conclusion of the eight-week block. Following this initial phase, the participants entered a four-week washout period, allowing their bodies to stabilize. This was followed by a two-week baseline period before they were assigned to the opposite diet for another eight weeks, culminating in a final round of retesting at the end of the second phase. It is an exceptionally thorough design for a nutritional intervention of this scale.
Both diets were specifically engineered and designed to meet the United Kingdom’s national dietary guidelines, as outlined by the official Eatwell Guide. To maintain strict control over the intervention, participants were provided with all of their meals and were explicitly instructed to refrain from consuming any other food or drink aside from water, though the researchers did accommodate participants by providing coffee and tea. The researchers made a deliberate, calculated effort to match the two dietary arms as closely as possible in terms of total calories, macronutrient distribution, dietary fiber, sodium content, saturated fat, and the intake of fruits and vegetables.
Under the hood, the structural composition of the two meal plans differed starkly in terms of food processing. The minimally processed diet consisted of wholesome, recognizable foods such as whole fruits, fresh vegetables, legumes, plain cuts of meat, eggs, and whole grains, all prepared with minimal industrial intervention. Conversely, the ultra-processed diet was constructed from items such as sweetened yogurts, packaged breakfast cereals, reconstituted meats, ready-made convenience meals, commercial snack bars, and diet soft drinks, all manufactured through standard industrial processes.
There was, however, a slight catch in the execution of the trial. The study was conducted under free-living, ad libitum conditions. This means that participants ate their meals at home and were permitted to consume as much or as little of the provided food as they wanted, provided they stuck exclusively to the foods they were given. While this design is commendable from an ecological validity perspective—reflecting how people actually eat in the real world—it is worth noting that it inherently increases the risk of non-compliance, particularly when examining outcomes related to body weight or body composition, given that participants ultimately relied on self-directed eating patterns within the provided framework.
When the results finally emerged, they offered a fascinating look at the interplay between food processing and human physiology. The minimally processed food diet led to greater weight loss, yielding a reduction of two percent of body weight compared to just one percent in the ultra-processed group. Furthermore, only the minimally processed diet produced statistically significant reductions in fat mass, overall body fat percentage, and visceral fat ratings. However, the researchers noted that these decreases were modest rather than dramatic, with body fat percentage, for instance, dropping by an average of 0.76 percent.
Beyond the shifts in body composition, participants following the minimally processed diet reported experiencing better control over their daily cravings. Perhaps most notably, their spontaneous daily energy intake ultimately decreased by about 330 calories compared to when they were consuming the ultra-processed diet. This distinction holds significant clinical and practical weight, as a calorie difference of approximately 300 calories per day is quite meaningful when attempting to generate or maintain the magnitude of a calorie deficit. At the same time, this finding hints at an important underlying mechanism: although the ultra-processed foods were nutritionally adequate on paper and matched for macronutrients, their physical texture, palatability, hyper-rewarding taste profile, or sheer ease of consumption may have unconsciously driven participants to eat more.
In terms of metabolic health, both diets successfully improved certain key biomarkers, including circulating triglycerides, fasting blood glucose, and cholesterol levels. However, these metabolic changes were relatively modest and demonstrated no statistically significant differences between the two study groups.
These findings carry several important takeaways for the broader discussion surrounding modern nutrition. It appears from these data that consuming an ultra-processed diet is not inherently disastrous for your body composition or metabolic health, provided that the diet still adheres closely to general health and nutritional guidelines. That is a significant and crucial caveat, however, because the study participants were still effectively ticking a lot of nutritional boxes—hitting fiber targets, balancing macronutrients, and following national health guidelines—despite the heavy processing of the foods they consumed.
Moreover, those participants were provided with all of their meals as part of a controlled intervention, a scenario that may not fully reflect how the average person interacts with ultra-processed foods in daily life, where such items are often consumed alongside poor overall diet quality, excessive calorie surpluses, and low physical activity.
Ultimately, while these findings offer a degree of reassurance for individuals who may not always have access to or time for exclusively minimally processed foods, they simultaneously underscore a vital warning. Even a nutritionally adequate, guideline-compliant ultra-processed diet has the potential to induce overeating, which can translate into adverse effects on body composition and long-term health if left unchecked.
As a general guideline for everyday life, making a conscious effort to consume mostly whole, minimally processed foods remains the optimal approach to human nutrition. At the same time, science suggests there is no need to overstress or experience anxiety if you find yourself consuming some ultra-processed foods here and there, particularly if you are still managing to adhere to fundamental nutritional principles and general health guidelines.
