Taste of Modern Diets: The Impact of Food Processing on Nutrient Sensing and Dietary Energy Intake

Ultra-processed Food and Obesity: What Is the Evidence?

PURPOSE OF REVIEW

Obesity is a growing global healthcare concern. A proposed driver is the recent increase in ultra-processed food (UPF) intake. However, disagreement surrounds the concept of UPF, the strength of evidence, and suggested mechanisms. Therefore, this review aimed to critically appraise the evidence on UPF and obesity.

RECENT FINDINGS

Observational studies demonstrate positive associations between UPF intake, weight gain, and overweight/obesity, more clearly in adults than children/adolescents. This is supported by high-quality clinical data. Several mechanisms are proposed, but current understanding is inconclusive. Greater UPF consumption has been a key driver of obesity. There is a need to change the obesogenic environment to support individuals to reduce their UPF intake. The UPF concept is a novel approach that is not explained with existing nutrient- and food-based frameworks. Critical analysis of methodologies provides confidence, but future observational and experimental research outputs with greater methodological rigor will strengthen findings, which are outlined.

Who consumes ultra-processed food? A systematic review of sociodemographic determinants of ultra-processed food consumption from nationally representative samples

Ultra-processed food (UPF) intake is associated with increased non-communicable disease risks. However, systematic reports on sociodemographic predictors of UPF intake are lacking. This review aimed to understand UPF consumption based on sociodemographic factors, using nationally representative cohorts. The systematic review was pre-registered (PROSPERO:CRD42022360199), following PRISMA guidelines. PubMed/MEDLINE searches (‘ultra-processed/ultraprocessed’ and ‘ultra-processing/ultraprocessing’) until 7 September 2022 retrieved 1131 results. Inclusion criteria included: observational, nationally representative adult samples, in English, in peer-reviewed journals, assessing the association between sociodemographics and individual-level UPF intake defined by the NOVA classification. Exclusion criteria included: not nationally representative, no assessment of sociodemographics and individual-level UPF intake defined by NOVA. Risk of bias was assessed using the Newcastle–Ottawa Scale (NOS). Fifty-five papers were included, spanning thirty-two countries. All thirteen sociodemographic variables identified were significantly associated with UPF intake in one or more studies. Significant differences in UPF intake were seen across age, race/ethnicity, rural/urbanisation, food insecurity, income and region, with up to 10–20% differences in UPF intake (% total energy). Higher UPF intakes were associated with younger age, urbanisation and being unmarried, single, separated or divorced. Education, income and socioeconomic status showed varying associations, depending on country. Multivariate analyses indicated that associations were independent of other sociodemographics. Household status and gender were generally not associated with UPF intake. NOS averaged 5·7/10. Several characteristics are independently associated with high UPF intake, indicating large sociodemographic variation in non-communicable disease risk. These findings highlight significant public health inequalities associated with UPF intake, and the urgent need for policy action to minimise social injustice-related health inequalities.

Beyond ultra-processed: considering the future role of food processing in human health

Food-based dietary guidelines have been the basis of public health recommendations for over half a century, but more recently, there has been a trend to classify the health properties of food not by its nutrient composition, but by the degree to which it has been processed. This concept has been supported by many association studies, narrative reviews and the findings from one randomised controlled feeding trial, which demonstrated the sustained effect of ultra-processed diets on increasing both energy intake and body weight. This has led to widespread speculation as to specific features of ultra-processed foods that promote increased energy intakes. Rising interest in the ultra-processed topic has led to proposals to include guidance and restrictions on the consumption of processed foods in national dietary guidelines, with some countries encouraging consumers to avoid highly processed foods completely, and only choose minimally processed foods. However, there remains a lack of consensus on the role of processed foods in human health when faced with the challenges of securing the food supply for a growing global population, that is, healthy, affordable and sustainable. There has also been criticism of the subjective nature of definitions used to differentiate foods by their degree of processing, and there is currently a lack of empirical data to support a clear mechanism by which highly processed foods promote greater energy intakes. Recommendations to avoid all highly processed foods are potentially harmful if they remove affordable sources of nutrients and will be impractical for most when an estimated two-thirds of current energy purchased are from processed or ultra-processed foods. The current review highlights some considerations when interpreting the dietary association studies that link processed food intake to health and offers a critique on some of the mechanisms proposed to explain the link between ultra-processed food and poor health. Recent research suggests a combination of higher energy density and faster meal eating rates are likely to influence meal size and energy intakes from processed foods and offers new perspectives on how to manage this in the future. In going beyond the ultra-processed debate, the aim is to summarise some important considerations when interpreting existing data and identify the important gaps for future research on the role of processed food in health.

Ultraprocessed Foods and Obesity Risk: A Critical Review of Reported Mechanisms

Epidemiologic evidence supports a positive association between ultraprocessed food (UPF) consumption and body mass index. This has led to recommendations to avoid UPFs despite very limited evidence establishing causality. Many mechanisms have been proposed, and this review critically aimed to evaluate selected possibilities for specificity, clarity, and consistency related to food choice (i.e., low cost, shelf-life, food packaging, hyperpalatability, and stimulation of hunger/suppression of fullness); food composition (i.e., macronutrients, food texture, added sugar, fat and salt, energy density, low-calorie sweeteners, and additives); and digestive processes (i.e., oral processing/eating rate, gastric emptying time, gastrointestinal transit time, and microbiome). For some purported mechanisms (e.g., fiber content, texture, gastric emptying, and intestinal transit time), data directly contrasting the effects of UPF and non-UPF intake on the indices of appetite, food intake, and adiposity are available and do not support a unique contribution of UPFs. In other instances, data are not available (e.g., microbiome and food additives) or are insufficient (e.g., packaging, food cost, shelf-life, macronutrient intake, and appetite stimulation) to judge the benefits versus the risks of UPF avoidance. There are yet other evoked mechanisms in which the preponderance of evidence indicates ingredients in UPFs actually moderate body weight (e.g., low-calorie sweetener use for weight management; beverage consumption as it dilutes energy density; and higher fat content because it reduces glycemic responses). Because avoidance of UPFs holds potential adverse effects (e.g., reduced diet quality, increased risk of food poisoning, and food wastage), it is imprudent to make recommendations regarding their role in diets before causality and plausible mechanisms have been verified.

Phyllanthi Fructus: A modal medicinal and food homologous item in quality evaluation

Phyllanthi Fructus is a highly unique medicine and food homologous item, which exhibits distinctive flavor, notable nutritional value, and abundant pharmacological activity. It has enormous potential in the creation of health products and pharmaceuticals. However, due to the unique laws of quality formation and transfer of Phyllanthi Fructus, its appearance, shape, chemical compositions, nutrients, and sensory flavors are frequently greatly influenced by botanical resources, the processing and storage conditions. As a result, the current quality evaluation model is difficult to meet the needs of Phyllanthi Fructus as a medicine and food homologous item in the development of diversified products. This paper constructs the hierarchical utilization mode of Phyllanthi Fructus based on its unique quality formation and transmission laws, explores the quality evaluation model for food-oriented use and medicinal-oriented use, respectively, and systematically describes the quality evaluation idea under diversified application scenarios. This paper aims to serve as a reference for the construction of a quality evaluation model suitable for the medicine and food homologous item of Phyllanthi Fructus.

Human nutritional intelligence underestimated? Exposing sensitivities to food composition in everyday dietary decisions

The social and cultural significance of food is woven into every aspect of our dietary behaviour, and it contributes to our complex interaction with food. To find order within this complexity scientists often look for dietary 'universals' - phenomena or basic principles that guide our food choice and meal size, irrespective of wider context. One such idea is that taste characteristics provide a signal for dietary composition (e.g., sweet taste signals carbohydrate). Others have suggested that behaviour is guided by learning and is based on associations that form between the flavour of a food and its post-ingestive effects. Despite a large body of research, evidence supporting both processes is equivocal, leading some to conclude that humans are largely indifferent to food composition. Here, we argue that human abilities to gauge the nutritional composition or value of food have been underestimated, and that they can be exposed by embracing alternative methods, including cross-cultural comparisons, large nutrition surveys, and the use of virtual portion-selection tools. Our group has focused on assessments of food choice and expected satiety, and how comparisons across everyday foods can reveal non-linear relationships with food energy density, and even the potential for sensitivity to micronutrient composition. We suggest that these abilities might reflect a complex form of social learning, in which flavour-nutrient associations are not only formed but communicated and amplified across individuals in the form of a cuisine. Thus, rather than disregarding sociocultural influences as extraneous, we might reimagine their role as central to a process that creates and imbues a 'collective dietary wisdom.' In turn, this raises questions about whether rapid dietary, technological, and cultural change disrupts a fundamental process, such that it no longer guarantees a 'nutritional intelligence' that confers benefits for health.

Ultra-Processed Food, Reward System and Childhood Obesity

Obesity and overweight are a major public health problem globally. Diet quality is critical for proper child development, and an unhealthy diet is a preventable risk factor for noncommunicable diseases (NCDs), such as obesity. Consumption of sugar-sweetened beverages and ultra-processed foods (UPFs) in childhood may increase the BMI/BMI z-score, body fat percentage, or likelihood of overweight. A strict feeding regulation system allows for sufficient food to be consumed to meet ongoing metabolic demands while avoiding overconsumption. This narrative review explores the issues of obesity and the regulation of food intake related to reward systems and UPF consumption. Nutrient composition alone cannot explain the influence of UPFs on the risk of obesity. Furthermore, the non-nutritional properties of UPFs may explain the mechanisms underlying the relationship with obesity and NCDs. UPFs are designed to be highly palatable, appealing, and energy dense with a unique combination of the main taste enhancer ingredients to generate a strong rewarding stimulus and influence the circuits related to feeding facilitation. How individual UPF ingredients influence eating behavior and reward processes remains not fully elucidated. To increase the knowledge on the relationship between UPFs and pediatric obesity, it may be useful to limit the rapid growth in the prevalence of obesity and subsequent related complications, and to develop new strategies for appropriate food and nutrition policies.

Scoping Review and Evidence Map of the Relation between Exposure to Dietary Sweetness and Body Weight-Related Outcomes in Adults

Numerous governmental and health organizations recommend reduced intake of added sugars due to the health risks associated with excess intake, including the risk of obesity. Some organizations further recommend avoiding dietary sweetness, regardless of the source. A scoping review and evidence map were completed to characterize the research that investigated associations between dietary sweetness and body weight. The aim was to identify and map published studies that have investigated total dietary sweetness, sweet food/beverages, sugar, or sweetener intake, and body weight-related outcomes and/or energy intake. Using preregistered search terms (osf.io/my7pb), 36,779 publications (duplicates removed) were identified from PubMed, Cochrane Library, and Scopus and screened for inclusion. Eligible studies were clinical trials, longitudinal cohorts, case-control studies, cross-sectional studies, and systematic reviews conducted among adults (age ≥18 y), which were performed to investigate associations between dietary sweetness, sweet foods/beverages, sugar, or sweetener (energetic or nonenergetic) intake and body weight, BMI, adiposity, and/or energy intake. A total of 833 eligible publications were identified, detailing 804 studies. Only 7 studies (0.9% of included studies; 2 clinical trials, 4 cross-sectional studies, and 1 with another design type) investigated associations between total dietary sweetness and body weight-related outcome and/or energy intake. An additional 608 (75.6%) studies investigated intakes of sweet foods/beverages, sugar, or sweetener, and body weight-related outcomes and/or energy intake, including 225 clinical trials, 81 longitudinal cohorts, 4 case-control studies, and 280 cross-sectional studies. Most studies (90.6%) did not measure the sweetness of the diet or individual foods consumed. Ninety-two (11.4%) publications reported data from studies on dietary patterns that included sweet foods/beverages alongside other dietary components and 97 (12.1%) systematic reviews addressed different but related research questions. Although there is a breadth of evidence from studies that have investigated associations between intakes of sweet foods and beverages, sugars, and sweeteners and body weight, there is a limited depth of evidence on the association between total dietary sweetness and body weight.

Harnessing Food Product Reviews for Personalizing Sweetness Levels

Sweet taste is innately appealing, ensuring that mammals are attracted to the sweetness of mother’s milk and other sources of carbohydrates and calories. In the modern world, the availability of sugars and sweeteners and the eagerness of the food industry to maximize palatability, result in an abundance of sweet food products, which poses a major health challenge. The aim of the current study is to analyze sweetness levels, liking, and ingredients of online reviews of food products, in order to obtain insights into sensory nutrition and to identify new opportunities for reconciling the palatability–healthiness tension. We collected over 200,000 reviews of ~30,000 products on Amazon dated from 2002 to 2012 and ~350,000 reviews of ~2400 products on iHerb from 2006 to 2021. The reviews were classified and analyzed using manual curation, natural language processing, and machine learning. In total, ~32,000 (Amazon) and ~29,000 (iHerb) of these reviews mention sweetness, with 2200 and 4600 reviews referring to the purchased products as oversweet. Oversweet reviews were dispersed among consumers. Products that included sucralose had more oversweet reviews than average. 26 products had at least 50 reviews for which at least 10% were oversweet. For these products, the average liking by consumers reporting oversweetness was significantly lower (by 0.9 stars on average on a 1 to 5 stars scale) than by the rest of the consumers. In summary, oversweetness appears in 7–16% of the sweetness-related reviews and is less liked, which suggests an opportunity for customized products with reduced sweetness. These products will be simultaneously healthier and tastier for a substantial subgroup of customers and will benefit the manufacturer by expanding the products’ target audience. Analysis of consumers’ reviews of marketed food products offers new ways to obtain informative sensory data.

The Importance of Food Processing and Eating Behavior in Promoting Healthy and Sustainable Diets

Numerous association studies and findings from a controlled feeding trial have led to the suggestion that "processed" foods are bad for health. Processing technologies and food formulation are essential for food preservation and provide access to safe, nutritious, affordable, appealing and sustainable foods for millions globally. However, food processing at any level can also cause negative health consequences that result from thermal destruction of vitamins; formation of toxins such as acrylamide; or excessive intakes of salt, sugar, and fat. Research on ultraprocessed foods centers on food composition and formulation. In addition, many modern food formulations can have poor nutritional quality and higher energy density. We outline the role of processing in the provision of a safe and secure food supply and explore the characteristics of processed foods that promote greater energy intake. Despite the potential for negative health effects, food processing and formulation represent an opportunity to apply the latest developments in technology and ingredient innovation to improve the food supply by creating foods that decrease the risk of overeating. Expected final online publication date for the Annual Review of Nutrition, Volume 42 is August 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Interrelations Between Food Form, Texture, and Matrix Influence Energy Intake and Metabolic Responses

Purpose of Review

Nutrition often focuses on food composition, yet differences in food form, texture, and matrix influence energy intake and metabolism. This review outlines how these attributes of food impact oral processing, energy intake, and metabolism.

Recent Findings

Food form has a well-established impact on intake, where liquids are consumed more than solids and semi-solids. For solids, texture properties like thickness, hardness, and lubrication, and geometrical properties like size and shape influence oral processing, eating rate, and intake. Food matrix integrity can influence nutrient and energy absorption and is strongly influenced by food processing.

Summary

Food texture and matrix play important roles in modulating energy intake and absorption. Future research needs to consider the often overlooked role of texture and matrix effects on energy and metabolic responses to composite foods and meals. Research is needed to understand how processing impacts macro- and micro-structure of food and its long-term impact on energy balance and health.

Influence of Sensory Properties in Moderating Eating Behaviors and Food Intake

Sensory properties inform likes and dislikes, but also play an important functional role in guiding food choice and intake behavior. Odors direct food choice and stimulate sensory-specific appetites and taste helps to anticipate calorie and nutrient content of food. Food textures moderate eating rate and the energy consumed to satiation and post-ingestive metabolism. We summarize how sensory cues moderate intake, and highlight opportunities to apply sensory approaches to improve dietary behavior. Salt, sweet and savory taste influence liking, but also influence energy intake to fullness, with higher taste intensity and duration linked to lower intake. Psycho-physical studies show it is relatively easy to rank taste intensities at different concentrations but more challenging to discriminate fat contents, and fat discrimination declines further when combined with high-taste intensity. Fat has low impact on sensory intensity, but makes significant contributions to energy content. Combinations of high taste and fat-content can promote passive energy over-consumption, and adding fat also increases energy intake rate (kcals/min), reducing opportunities to orally meter consumption. Consumers adapt their oral processing behaviors to a foods texture, which can influence the rate and extent of energy intake. Understanding how texture influences eating behaviors and bolus formation, affords new opportunities to impact eating rate, energy intake and metabolic response to food. Food formulation has traditionally focused on composition and sensory appeal. Future research needs to consider the role of sensory properties in moderating consumer interaction with their food environment, and how they influence calorie selection, and shape our eating behaviors and intake.

Nutrition research challenges for processed food and health

Existing highly processed food (HPF) classification systems show large differences in the impact of these foods on biochemical risk factors for disease. If public health nutrition is to consider the degree of food processing as an important element of the link between food and health, certain gaps in research must be acknowledged. Quantifying the food additive exposure derived from HPFs is a task made challenging by the lack of data available on the occurrence and concentration of additives in food and the degree to which the natural occurrence of additives in unprocessed foods confounds exposure estimates. The proposed role of HPFs in health outcomes could also be associated with altered nutrient profiles. Differences exist within and between HPF classification systems in this regard and there are conflicting data on the impact of controlling for nutrient intake. Furthermore, research is needed on how the sensory aspects of HPFs contribute to energy intake. Current data suggest that high energy intake rate may be the mechanism linking HPFs and increased energy intake. A high priority now is to clarify the basis of definitions used to categorize foods as highly processed and, in a constructive sense, to distinguish between the contributions of nutrients, additives and sensory properties to health.