Eating Ultra-Processed Foods and Higher Risk of Obesity: A Summary Review

Obesity has been identified as a complex multifactorial disease, the antechamber for the onset of pathological conditions such as diabetes, coronary heart disease, stroke, hypertension, and various tumors affecting the colon, breast, and prostate. Currently, it represents one of the main causes of preventable death: approximately 100,000–400,000 deaths have been estimated every year in the United States, and there has been an increase in health spending amounting to 140–215 billion dollars [1,2,3].The exponential increase in obesity over the last 30 years indicates that weight gain may depend on individual choices in response to the economic environment. The literature has identified several factors that potentially play a crucial role related to the increase in obesity. Prominent among these are higher income levels, the technological evolution of the food industry, the increased prevalence of fast-food restaurants and commercials inducing the population to purchase junk food, possible changes in time preferences, declining smoking rates, an increased prevalence in major depression, and changes in health insurance [4]. To identify dietary factors related to weight gain and obesity, researchers have focused on the choice of dietary patterns [5]. Several epidemiological studies indicate a strong inverse correlation between adherence to a healthy and balanced dietary protocol, such as the Mediterranean model, and an increase in cardiometabolic risk [6,7,8]. Conversely, a diet characterized by highly processed foods is closely associated with obesity and related metabolic comorbidities [9,10]. An understanding of the impact of ultra-processed foods (UPFs) on health and as a risk factor for diet-related diseases, disorders, and conditions is rapidly emerging. In modern society, the role of UPFs proposed by the food industry contrasts with traditional dietary models that promoted the consumption of whole meal products and 0 km foods and emphasized the importance of the locality and seasonality of foods [11,12]. In recent years, the whole food production chain has been significantly influenced by the evolution of technological advances, which have led to the greater accessibility and commercialization of UPFs. The sophistication of production processes has structurally and sensorially modified the nutritional content of foods [13,14] in proportion to the degree of transformation. UPFs are therefore “empty” from a nutritional point of view, but full of added food substances such as sugars, salt, protein isolates, syrups with high fructose content, maltodextrins, and additives such as colorants, flavorings, artificial sweeteners, and thickeners used to enhance the taste of the product, making it palatable, easily usable, and economically accessible. Recently, the view that it is the processing of products that is closely associated with the rise of the obesity epidemic has been gaining more and more credence. This has been verified and supported by a review of prospective cohort studies conducted on more than one million subjects [4]. This led to the development of the NOVA food classification system according to the transformation process, which allows us to identify the dietary drivers related to the increased risk of obesity [15,16,17]. The NOVA classification system provides for a grouping of foods into four categories depending on the degree and extent of processing used [18,19]: unprocessed or minimally processed foods; processed culinary ingredients; processed foods that are produced by adding salt, oil, sugar, or other culinary ingredients to minimally processed foods and processed foods; and finally, at the pinnacle of the processing spectrum, ultra-processed foods (UPFs) [15,16,17,20]. Several studies highlight that UPF consumption is increasing exponentially in recent years and characterizes more than half of the daily calories in US [16], Canadian [19], or British [21] diets. UPF abuse leads to a nutritionally unbalanced diet, rich in calorie-dense foods, saturated fats, sugar, and salt, but low in fiber and micronutrients [21], with a potentially high impact on health [22]. In light of this evidence, the purpose of this narrative review lies in researching the correlation between ultra-processed foods and the increased trend of obesity and related cardiometabolic outcomes.

The spread of obesity represents a great concern for health, as it is classified as the fifth cause of death worldwide [36]. The latest studies focus on a new perspective: the obesity epidemic seems to derive from a high intake of ultra-processed foods (UPFs). These data emerge from a review of prosthetic cohort studies that analyzed more than 1 million people. UPFs are industrial food formulations that undergo a processing and transformation process through the addition of various ingredients such as simple sugars, fats, salt, and other chemicals such as chemical additives, combined with whole or non-whole foods with the aim of increasing their level of palatability, prolonging their shelf life, and making them convenient and easily available [59,60].

In a recent systematic review, several prospective studies focused on the association between the consumption of ultra-processed foods and the incidence of obesity and cardiometabolic diseases in the adult population [61,62,63,64,65,66]. In most of the articles analyzed, there is an increasing trend of obesity and complications (such as dyslipidemia, hypertension, type 2 diabetes mellitus, and metabolic syndrome) linked to excessive caloric intake, characterized predominantly by packaged and ultra-processed foods to the detriment of a diet rich in whole meal products, fruit, vegetables, and fresh foods.

In 2010, a NOVA classification model was created, which divides foods into four groups based on the degree and type of food processing and transformation [19,67,68]. The first group includes foods that have not undergone a transformation process or have done so only to a minimal extent: for example, processes aimed at ensuring the edibility, suitability for consumption and conservation, safety, and palatability of altered plants and animals (Figure 2).

The second group includes processed ingredients such as butter, oils, salt, and sugar used to make dishes more palatable. The third group includes processed foods, i.e., products to which two/three ingredients from the first and second groups are added to prolong their shelf life and improve their organoleptic quality. Finally, the last classification includes ultra-processed foods (UPFs), i.e., food formulations characterized by the presence of five or more modified or unmodified substances extracted from other foods and combined with minimally whole and non-whole foods, and food additives that improve sensorial quality and prolong shelf life. These include packaged products, breakfast cereals, sweet and savory snacks, packaged bread, margarine, reconstituted meat foods, ready-to-eat soups, ready-to-eat frozen foods, and carbonated and distilled alcoholic beverages. The consumption of UPF foods is spreading exponentially, resulting in nutritional deficiencies (fiber, vitamins, and mineral salts) and a high caloric intake. Several studies show a positive correlation between the consumption of UPF foods and increased rates of obesity and cardiometabolic risk among adult and child populations [61,69,70] (Table 1).

The demand for UPF foods has increased over time, and the causes are to be found in the lifestyle of today’s society: intense work rhythms, the lack of time, and quick meal management lead to a greater demand for foods that can be easily consumed during work activity [8,71,72]. This leads to an unconscious consumption that alters neural and digestive functions, which dysregulate hunger perception and satiety levels, which in turn leads to excessive consumption [73,74]. Furthermore, it has been shown that these foods—precisely because they are poor from a nutritional point of view (in particular in fiber, micronutrients and bioactive compounds [21,63]) but rich in saturated and trans fatty acids, sodium, and refined sugars—reduce satiety levels and therefore increase the glycemic response, altering the insulin response [75], which leads to a greater search for food, favoring a greater energy intake [76] and establishing a serious vicious circle which over time leads to excess weight.

The picture presented determines cardiovascular, metabolic, and blood pressure outcomes that are risky for health. In most UPFs, the salt content is high, and this contributes to increasing the risk of developing hypertension [77]. As previously mentioned, the addition of simple sugars also alters fructose metabolism, in particular favoring insulin resistance first at the liver level and then at the systemic level, exacerbating low-grade inflammation. To overcome insulin resistance and restore glycemic levels, pancreatic β cells produce a greater amount of insulin through a negative feedback mechanism, leading to structural damage and reduced functionality [78]. Furthermore, the excessive consumption of UPFs also leads to a modification of the lipid structure due to the high presence of saturated and trans fatty acids, compromising the catabolism of very-low-density lipoproteins (VLDL-C) and increasing triglycerides in the blood and reducing HDL cholesterol [79]. Finally, the presence of chemical additives, preservatives, and synthetic antioxidants further worsens the clinical picture [80,81]. The packaging used for UPF foods is characterized by releasing chemicals such as bisphenol A, which is harmful to the endocrine system (Figure 2) [82,83,84].

UPF foods differ from non-UPF foods not only in their composition and type of production, but also in their destination. As previously reported, the aim is to obtain artificial, ready-made, quick, easy-to-take, highly palatable foods produced with cheap ingredients [21,67,68]. The production of UPF products contrasts with the recommendations of the dietary model proposed by the Mediterranean diet, which limits the consumption of packaged, processed, and ultra-processed foods. From a nutritional point of view, UPFs appear very unbalanced, composed mostly of ingredients that should be limited, such as added sugars, salt, and saturated and trans fats, and poor in fiber, vitamins, and mineral salts [19]. To paraphrase Paracelsus, it is the dose that makes the poison. In the Mediterranean model, in fact, the consumption of these foods is not demonized, but their intake is limited. Numerous studies conducted on a national scale have recorded a close co-occurrence between the consumption of UPF and the nutritional inadequacy of diets [85]. The appearance of pathological conditions and metabolic complications does not depend only on an excessive daily intake, but on the entirety of the serious nutritional imbalance that derives from the excessive use of these foods. In fact, manufacturing processes generate an inevitable loss of important nutrients for our body and transform others into harmful substances; this happens, for example, with the hydrogenation of polyunsaturated fats. The risk linked to the manipulation and transformation of the food matrix is not limited only to the addition of ingredients such as sugars, vegetable oils, protein isolates, milk powder, additives, emulsifiers etc., but to the formation and release of harmful substances from synthetic packaging [86]. The physico-chemical profile of UPF foods is very complex, so it is reductive to focus on the analysis of a small group of nutrients, which can overlook the evaluation of the substances that are released by the type of ultra-process used. In fact, the analysis often hides the modification at the molecular level to which these products are subjected. Research is moving towards the identification not only of the nutritional profile, but also of composition, chemical structure, and unclear mechanisms that impact health [87]. How does the new formation of toxic substances, chemical hydrogenation, and the presence of synthetic substances influence our biological systems? What are the consequences? At this point, we need to introduce the term “reconstitution”: ingredients used in the manufacturing process are reconstituted through various operations such as the hydrogenation of fats, the extrusion of cereals, and the mechanical extraction of meat which modify the chemical–physical structure of the food matrix, generating new substances [75,76]. The list of ingredients present in UPF foods is very long, among which we also find colorants, artificial sweeteners such as aspartame, saccharin, and acesulfame K, and emulsifiers [88,89]. The use of these substances is not accidental; in fact, they make the product very tasty; they create addiction, leading to greater consumption [65]. They are mistakenly called “foods”, but in reality they are anything but nutritious compared to minimally processed or fresh/whole foods which maintain their own nutritional characteristics. It would be more appropriate to define them as non-nutrient in terms of the substances that are lost and degraded during the processing operations. When the diet is particularly rich in these non-nutrients that replace unprocessed foods, the impact on health is harmful. Ultimately, it is possible to distinguish two dietary models: the first includes minimally processed products, i.e., products or dishes prepared at home or artisanally in restaurants with few processed ingredients or with the addition of processed foods, while the second model includes UPF foods, i.e., drinks and ultra-processed foods such as ready meals and fast food distributed on a large scale [90]. Supermarket shelves are full of this wide range of UPF foods, sweet and savory, and drinks of all kinds, accompanied by claims that attract the attention of the consumer, who is less and less attentive to food quality and consumes his meal quickly during his lunch break. Therefore, the background into which UPFs are inserted contrasts with the model of the Mediterranean diet, which on the contrary encourages consuming meals as a family, around a well-laid table that offers healthy and tasty foods, prepared together. Marketing strategies prove to be very effective in promoting these products and in their combination, such as hamburgers, chips, and carbonated drinks rich in added sugars or snacks and fruit juices, which contain everything other than fruit. The damage that these products generate in the long term on the health of those who feed themselves totally or almost entirely with these products is worrying: a randomized and controlled study recorded that subjects who consumed 80% of their calories from these non-nutrients had a high caloric intake, an increase in adipose tissue, and ultimately severe malnutrition [91] (Table 2) In fact, some studies have revealed a positive correlation between the ultra-processed dietary model and the nutritional scarcity of the diet [92]. Finally, further perspectives are shown in meta-analyses and cohort studies which demonstrate what was previously asserted: dose–response models show in fact that the UPF model can potentially cause damage and become dangerous, leading to the onset of chronic non-communicable diseases and therefore to an increase in mortality when the consumption of these foods becomes dominant.

In conclusion, the aspect that should not be underestimated is the market strategy implemented by companies that produce UPF foods, which use advertising policies aimed at promoting and legitimizing their products, regardless of their nutria-chemical composition and therefore quality. Tighter regulation of these foods is necessary and urgent, in terms of evaluating the nutritional composition and the impact that this dietary model produces on public health. UPF dietary patterns should be reduced, especially in countries that consume them widely and with a view to primary and secondary prevention, especially in the most sensitive age groups, defining safe cut-offs for health [93] (Table 2).

Addressing the global epidemic of obesity requires multifaceted approaches, and public health policies play a pivotal role in shaping individuals’ dietary habits. One critical aspect is curbing the consumption of ultra-processed foods, which are laden with unhealthy additives, sugars, and fats. Governments can implement policies aimed at reducing the availability and accessibility of ultra-processed foods. This includes imposing taxes on sugary beverages and snacks, restricting marketing to children, and regulating portion sizes in food outlets. In addition, establishing clear nutritional guidelines can help consumers make informed choices [48]. Governments can collaborate with health experts to develop guidelines that prioritize whole, minimally processed foods, while discouraging the consumption of ultra-processed options. Educating the public about the health risks associated with ultra-processed foods is essential. Public health campaigns can highlight the adverse effects of excessive sugar, salt, and trans fats on overall health, particularly in relation to obesity, cardiovascular diseases, and diabetes. Also, improving food labeling is crucial for empowering consumers to make healthier choices. Clear and concise labeling that indicates the presence of additives, excessive sugars, and unhealthy fats can help individuals identify ultra-processed products and opt for healthier alternatives. Encouraging the consumption of whole foods, such as fruits, vegetables, whole grains, and lean proteins, is fundamental [46]. Initiatives that make these foods more affordable, accessible, and appealing can shift dietary preferences away from ultra-processed options. It is important, also, to have school-based interventions; indeed, schools play a significant role in shaping children’s dietary habits. Implementing nutrition education programs and ensuring that school meals adhere to health guidelines can promote healthier eating behaviors from a young age [91]. Furthermore, engaging communities through initiatives like farmers’ markets, community gardens, and cooking classes can foster a culture of healthier eating. These interventions not only provide access to fresh, whole foods but also empower individuals with the knowledge and skills to prepare nutritious meals at home. Holding food manufacturers accountable for the nutritional quality of their products is essential. Encouraging reformulation to reduce the levels of added sugars, sodium, and unhealthy fats in processed foods can contribute to improving their overall dietary quality. Combating obesity and reducing the consumption of ultra-processed foods requires a comprehensive approach that encompasses policy changes, education, community involvement, and industry cooperation. By implementing these strategies collectively, societies can promote healthier food environments and mitigate the burden of obesity-related diseases [92].

Addressing the complex issues of obesity and ultra-processed food consumption presents numerous challenges, but also opportunities for innovative research and policy development. One of the greatest challenges is the unequal distribution of resources and access to healthy foods. Low-income communities often have limited access to fresh, nutritious foods and may rely heavily on cheap, ultra-processed options [90]. Addressing these disparities requires multifaceted approaches that consider social, economic, and environmental factors. In addition, the powerful influence of the food industry presents a significant barrier to promoting healthier food environments. Marketing tactics, product placement, and lobbying efforts can perpetuate the consumption of ultra-processed foods, making it challenging to implement effective policies. Future interventions must navigate this landscape, while advocating for public health [91]. Changing dietary behaviors is inherently challenging, requiring sustained motivation, support, and access to resources. Many individuals face barriers such as cultural preferences, lack of cooking skills, and ingrained habits that make it difficult to adopt healthier eating patterns. Future interventions should incorporate behavioral science principles to facilitate lasting change [84]. Ultra-processed foods often have a higher environmental footprint compared to whole, minimally processed alternatives. Addressing obesity while promoting environmental sustainability requires a balance between health outcomes and ecological considerations. Future research should explore strategies for promoting sustainable diets that benefit both human health and the planet. In addition, individual genetic predispositions and biological factors can influence susceptibility to obesity and metabolic disorders [92,93]. Understanding the interplay between genetics, metabolism, and dietary factors is essential for personalized approaches to obesity prevention and treatment. Emerging research areas such as nutrigenomics offer insights into how genetic variation affects responses to dietary interventions. Evaluating the effectiveness of policy interventions is crucial for refining strategies and maximizing their impact. Robust evaluation methods, including longitudinal studies and randomized controlled trials, are needed to assess the outcomes of public health policies targeting obesity and ultra-processed food consumption. Additionally, translating research findings into actionable policies requires collaboration between policymakers, researchers, and stakeholders. Also, the proliferation of digital health technologies offers new avenues for addressing obesity and promoting healthier food choices. Mobile apps, wearable devices, and online platforms can facilitate behavior tracking, provide personalized feedback, and deliver educational content to support individuals in managing their weight and making healthier dietary choices.

In the coming years, research should continue to address these challenges, while exploring innovative approaches to promoting healthier food environments and reducing the burden of obesity-related diseases. Collaboration across disciplines, sectors, and stakeholders will be essential for developing comprehensive solutions that improve public health outcomes on a global scale.

In conclusion, the link between ultra-processed food consumption and obesity is undeniable, with a mounting body of evidence highlighting the detrimental effects of these foods on public health. The proliferation of ultra-processed foods in modern diets, characterized by their convenience, affordability, and palatability, has contributed to the global obesity epidemic. These foods, laden with unhealthy additives, sugars, and fats, disrupt normal hunger and satiety cues, leading to excessive calorie consumption and metabolic dysregulation. Behavioral science principles should be integrated into interventions to facilitate lasting behavior change, while efforts to promote sustainability must balance health outcomes with environmental considerations. Personalized approaches to obesity prevention and treatment, informed by genetics and metabolism, offer promising avenues for future research. Robust evaluation methods are needed to assess the effectiveness of policy interventions, and digital health technologies can enhance efforts to promote healthier food environments and empower individuals to make informed choices. In the face of these challenges, continued collaboration and innovation are essential for developing comprehensive solutions that improve public health outcomes and reduce the burden of obesity-related diseases on a global scale.

Conceptualization, M.M., R.P. and G.M.; methodology, A.M. (Antonietta Monda) and M.I.d.S.; software, F.M.; validation, P.L., A.D., M.M. and G.M.; formal analysis, I.V.; resources, V.M., S.A., M.C. and M.D.P.; data curation, F.M. and A.M. (Antonietta Messina); writing—original draft preparation, A.M. (Antonietta Monda) and M.I.d.S.; writing—review and editing, R.P. and G.M.; visualization G.D.M., M.L.M. and S.C.; supervision, M.M.; project administration, G.M. and M.M.; funding acquisition, M.M. All authors have read and agreed to the published version of the manuscript.

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

The authors declare no conflicts of interest.

This research received no external funding.