Unhealthy diets are a major cause of death and disability, exacerbating the risk of obesity, cardiovascular disease, certain cancers and type 2 diabetes(Reference Abbafati, Machado and Cislaghi1). These poor-quality diets are typically characterised by the overconsumption of less healthful foods and nutrients (e.g. processed meats, refined grains and sugar-sweetened beverages, sugar, saturated fat and sodium) and the inadequate consumption of health promoting foods and nutrients (e.g. fruits, vegetables, wholegrains, legumes, nuts, seeds, fibre, unsaturated fats and potassium)(Reference Micha, Shulkin and Peñalvo2). While these individual dietary components can have important effects on specific disease risks (e.g. saturated fat and cardiovascular disease risk), it is a persons’ overall dietary pattern that shows the strongest link with health(Reference Miller, Webb and Cudhea3). Unfortunately, despite continuous efforts to promote healthier food choices, most peoples’ diets remain below optimal levels(Reference Miller, Webb and Cudhea3).
Compounding this health burden, food systems exert a considerable strain on the environment. According to some estimates, the global food system accounts for around a third of all greenhouse gas emissions (GHGe)(Reference Crippa, Solazzo and Guizzardi4), approximately 70 % of all freshwater use(5), and is responsible for 78 % of fresh and oceanic eutrophication(Reference Poore and Nemecek6). Moreover, agricultural practices are the leading cause of biodiversity loss worldwide(Reference Tilman, Clark and Williams7). Clark et al. (Reference Clark, Domingo and Colgan8), estimated that even in a scenario where all fossil fuel emissions were immediately halted, the 1·5°C Paris Agreement target would remain elusive without substantial changes to the food system. There is now a broad consensus that improving both human and planetary health will require us to change the way we produce and consume food.
Sustainable healthy diets are defined as ‘dietary patterns that promote all dimensions of individuals’ health and wellbeing; have low environmental pressure and impact; are accessible, affordable, safe and equitable; and are culturally acceptable’(9). This definition is complex and incorporates aspects relating to health and environmental protection, as well as social and economic considerations. The precise makeup of a sustainable diet depends on the country context. That said, most organisations agree on some fundamental principles: only eat to meet ones’ energy needs, prioritise plant-based foods and moderate intakes of animal sourced foods, especially ruminant meat, limit the consumption of energy-dense and nutrient poor foods and minimise food waste(9).
Transitioning to a more sustainable food system requires actions throughout the food chain, from farmers to consumers(Reference Hoek, Malekpour and Raven10,Reference Caleffi, Hawkes and Walton11) . A central focus of this transition will be changing the way people eat. For instance, studies suggest that even modest changes to peoples’ diets could bring substantial health(Reference Fadnes, Økland and Haaland12) and environmental benefits(Reference Hoolohan, Berners-Lee and McKinstry-West13). But changing the way people eat is notoriously difficult, especially at a population level(Reference Gillison, Verplanken and Barnett14). Food choices are complex, multifaceted behaviours influenced by a multitude of interacting individual, interpersonal, environmental and policy-related factors (Fig. 1)(Reference Gillison, Verplanken and Barnett14,Reference Symmank, Mai and Hoffmann15) . To effectively promote healthy and sustainable diets, it is essential that researchers and practitioners acknowledge the myriad of factors influencing peoples’ eating behaviours.
Fig. 1 Individual, interpersonal, environmental and policy-related factors influencing food choices, adapted from Symmank et al. (Reference Symmank, Mai and Hoffmann15)
Most consumers rate health as a leading motive for their food choices(Reference Connors, Bisogni and Sobal16,Reference Cunha, Cabral and Moura17) . In contrast, despite gaining traction among consumers, food sustainability remains far less influential(Reference Kenny, Woodside and Perry18). A key factor underpinning these food choice motives is consumers perceptions of healthy and sustainable eating. While consumers often say health is a key driver of what they put on their plates, how health and healthy eating are conceptualised will determine how this motivation is expressed(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20) . Thus, peoples’ perceptions of healthy and sustainable eating may act as an important determinant of their food choices.
Moreover, understanding consumers perceptions of healthy and sustainable eating is critical to gauge the effectiveness of promotional messaging and to ensure that future messages align with peoples’ values and beliefs. Thus, insights into how people interpret healthy and sustainable eating can provide valuable guidance for policymakers. Armed with this knowledge, practitioners can design interventions and policies that better connect with the way consumers think about food, health and sustainability.
The aim of this review was to examine how consumers interpret healthy and sustainable eating. The evidence presented in this review will focus on adults in high-income countries, with a specific emphasis on studies conducted in the UK and Ireland where possible. While we assessed both quantitative and qualitative research, a particular emphasis was placed on qualitative studies as they provided a more in-depth exploration of the different meanings people associate with healthy and sustainable diets. As most consumers perceive healthy eating and sustainable eating as distinctive concepts(21), we examined each of these separately before examining how consumers conceptualised them as a combined construct.
Consumers’ interpretation of healthy eating
Most people recognise a link between what they eat and their health. But consumers understanding of this connection is complex, as health and healthy eating are conceptualised in a variety of ways. Understanding these varying interpretations could aid health promoters design interventions that are more aligned with peoples’ everyday food practices, facilitating dietary change in a more meaningful way. Quantitative research suggests that most consumers are reasonably aware of healthy eating principles when pre-coded answers are provided(22,23) . However, these quantitative findings fail to capture the vast and varied meanings people associate with healthy eating. To understand these complex interpretations, one must look to the qualitative literature.
Several reviews have attempted to synthesise the qualitative literature examining how adults in high-income countries conceptualise healthy eating(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Paquette24) . These studies find that consumers interpret healthy eating as a multidimensional concept, combining aspects consistent with formal dietary guidance (e.g. a diet high in fruits and vegetables) with concepts outside traditional nutrition discourse (e.g. enjoyment of food)(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20) . Here we have categorised the different ways consumers conceptualise healthy eating into three broad areas: (1) Food categorisation, (2) Ways of eating and (3) Outcomes.
Food categorisation: foods, nutrients and food characteristics
People categorise food in several context specific ways(Reference Blake, Bisogni and Sobal25). One of the most common of these is to categorise foods as either ‘healthy’ or ‘unhealthy’(Reference Blake, Bisogni and Sobal25). Healthy eating, therefore, is almost always described through the categorisation of specific foods, food groups and/ or nutrients(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20) . However, consumers also categorise the healthiness of foods based their specific characteristics (e.g. fresh, natural, unprocessed, homemade)(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Hazley, Stack and Kearney26) .
In general, the foods and nutrients that consumers label as ‘healthy’ and ‘unhealthy’ align with dietary guidelines(Reference Herforth, Arimond and Álvarez-Sánchez27). Participants almost always emphasise the consumption of fruits and vegetables(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Paquette24) , as well as wholegrains, legumes, fish, nuts and seeds(Reference Klink, Härtling and Schüz20,Reference Hazley, Stack and Kearney26) . In contrast, consumers consistently describe ‘junk’, or processed foods (e.g. sugar-sweetened beverages) that are high in fat, sugar and salt as unhealthy(Reference Klink, Härtling and Schüz20,Reference Hazley, Stack and Kearney26) . Some foods, like meat, especially red meat, garner more mixed opinions(Reference Klink, Härtling and Schüz20,Reference Paquette24) . For some, meat is perceived as a healthy and ‘natural’ source of protein(Reference Paquette24,Reference Gillison, Lannon and Verplanken28) . For others, meat has more negative health connotations, being described as fatty or ‘bad’ for cholesterol(Reference Hazley, Stack and Kearney26,Reference Gillison, Lannon and Verplanken28) . Some research suggests that the perceived healthiness of meat differs by gender, with women being more likely to view meat as unhealthy and men more likely to perceive it as essential and a key source of protein(Reference Gillison, Lannon and Verplanken28).
Consumers consistently view processed, ready-made and fast foods as synonymous with unhealthy eating, whereas fresh, home-cooked meals are seen as pillars of a healthy diet(Reference Klink, Härtling and Schüz20,Reference Hazley, Stack and Kearney26) . Consumers negative perception of processed foods often stems from the presence of additives or other negatively perceived components (e.g. gluten) that are viewed as unnatural(Reference Klink, Härtling and Schüz20,Reference Hazley, Stack and Kearney26) . For many, the healthiness of a food is equated with how natural it is perceived(Reference Klink, Härtling and Schüz20,Reference Román, Sánchez-Siles and Siegrist29) . These naturalness evaluations are based on three main criteria, a food’s farming origin (e.g. organic or non-organic), method of production (e.g. presence of artificial additives) and the specific characteristics of the final product (e.g. how fresh it is perceived)(Reference Román, Sánchez-Siles and Siegrist29). While there may be some merit to limiting the consumption of ultra-processed foods high in fat, sugar and salt(Reference Taneri, Wehrli and Roa-Díaz30), the belief that a foods healthfulness is determined by its ‘naturalness’ is less well founded(Reference Sanchez-Siles, Roman and Fogliano31).
In addition to the ‘healthy’ and ‘unhealthy’ labels, many consumers also categorise food using moralistic language, describing foods’ as ‘good’ or ‘bad’(Reference Klink, Härtling and Schüz20,Reference Hazley, Stack and Kearney26) . This moral framing is indicative of the inner turmoil experienced by individuals as they grapple with the desire to make the ‘right’ food choices(Reference Delaney and McCarthy32). Such moral dichotomy may inadvertently cast the pleasure and satisfaction derived from food in a negative light, further intensifying feelings of guilt when one falls short of the prevailing standards of healthy eating(Reference Delaney and McCarthy32,Reference Coveney33) . Health advocates should aim to counteract the negative moral implications of traditional healthy eating initiatives by designing messages that highlight the pleasure and satisfaction derived from consuming nutritious foods, helping to create a more positive perception of healthy eating(Reference Bédard, Lamarche and Grégoire34).
Ways of eating: balance, variety and restraint
As with many dietary guidelines, consumer perceptions of healthy eating are heavily shaped around concepts like dietary variety, balance and self-control or restriction(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Paquette24) . Consumers often describe a healthy diet as varied, including a mixture of different foods, food groups and/ or nutrients(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Paquette24) . For many, dietary variety is closely connected to the concept of ‘balanced’ eating, with healthy diets containing a ‘balance’ of food groups (i.e. eating fruit and vegetables, meats and starches) and/ or nutrients (i.e. macro- and micro-nutrients)(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Paquette24) . These descriptions are consistent with messages used in many dietary guidelines. For instance, the Irish dietary guideline recommends ‘eating a wide variety of nourishing foods’(35).
However, consumers conceptualise ‘balanced’ eating in multiple ways, with many interpretations straying further from recommendations(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Paquette24) . In addition to dietary variety, balanced eating is also used to describe a compensatory behaviour, in which unhealthy food choices are ‘balanced’ with healthy ones(Reference Bisogni, Jastran and Seligson19,Reference Paquette24,Reference Hollywood, Cuskelly and O’Brien36) . This compensatory behaviour is sometimes described on a day-to-day basis, where overconsumption on one day is balanced with less on the next, or it is portrayed over the course of a day, in which healthy meals compensate for the consumption of ‘treats’(Reference Bisogni, Jastran and Seligson19,Reference Paquette24) . For example, Hollywood et al. (Reference Hollywood, Cuskelly and O’Brien36), found that one of the approaches consumers use to construct a healthy food shop is to offset their selection of unhealthy products (e.g. sugary snack foods) by purchasing healthy items (e.g. fruits and vegetables).
The term balanced is also mentioned in combination with concepts such as moderation and restraint or self-control(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20) . Several studies highlight how many consumers view healthy eating as something that requires constant vigilance(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20) . People appear to manage these feelings of restraint by balancing them with rewards of non-restrictive or unhealthy intakes(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20) . Bouwman et al. (Reference Bouwman, te Molder and Koelen37) found that participants often felt being overly restrictive would be to deny oneself pleasure. Thus, even health-conscious eaters strive to compensate for unhealthy consumption to achieve a health-pleasure balance(Reference Bisogni, Jastran and Seligson19,Reference Bouwman, te Molder and Koelen37) .
These findings are consistent with the Compensatory Health Belief Model, which suggests that people overcome value conflicts (e.g. health v. pleasure) through the believe that the negative effects of unhealthy behaviours can be offset by engaging in healthy behaviours(Reference Rabiau, Knäuper and Miquelon38). An issue with this belief system is that consumers perceptions of moderate consumption may be well above what is recommended. For instance, vanDellen et al. (Reference vanDellen, Isherwood and Delose39), found that people defined ‘moderation’ based on their personal consumption habits. In other words, the more someone consumed, the larger they estimated a moderate intake. This means that regardless of the amount consumed, people may implicitly view their intake of unhealthy products as appropriate as it is less than what they perceive as ‘moderate’(Reference vanDellen, Isherwood and Delose39). Thus, without clear guidance on what terms like moderate or balanced mean, messages promoting these concepts may be subject to misinterpretation.
Outcomes: physical and mental
Several studies have highlighted how consumers also conceptualise healthy eating in terms of the consequences or outcomes they associate with better or worse eating(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Hazley, Stack and Kearney26) . These can be physical health outcomes, such as energy, weight, disease or condition management/ prevention, or athletic performance; or they can be mental health outcomes, like psychosocial or spiritual well-being, satisfaction, or enjoyment(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20) .
By far the most common physical outcome people associate with healthy eating is body weight(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Paquette24) . For many, healthy eating is synonymous with weight loss or the maintenance of an ‘ideal’ weight(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Paquette24) . Managing one’s weight is an integral reason why moderation or self-control are considered central components of a healthy diet(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Paquette24,Reference Hazley, Stack and Kearney26) . In some cases, this connection with body weight may lead some to be optimistic about their diet, believing it is healthier than it truly is(Reference Hazley, Stack and Kearney26,Reference Sørensen and Holm40) . In other words, some people may use their perceived health characteristics to determine the healthiness of their diet (i.e. ‘if I feel good and aren’t overweight then my diet must be healthy’)(Reference Sørensen and Holm40). The physical outcomes people associate with healthy eating tend to differ by life stage. For instance, younger adults are more likely to see eating healthily as a way to optimally ‘fuel’ their athletic or professional activities(Reference Bisogni, Jastran and Seligson19,Reference Bech-Larsen and Kazbare41) . However, older adults are more likely to view healthy eating as way to manage their health conditions (e.g. to reduce their cholesterol)(Reference Bisogni, Jastran and Seligson19,Reference Bech-Larsen and Kazbare41) . This distinction is likely shaped by the different health experiences that younger and older adults encounter throughout their lives. As younger adults rarely experience serious health conditions, the benefits of eating healthily are primarily shaped by short term goals, like maintaining energy or feeling physically and mentally well(Reference Bisogni, Jastran and Seligson19,Reference Bech-Larsen and Kazbare41) . In contrast, older adults’ perceptions of healthy eating is often influenced by their health status and their desire to maintain independence and not be a burden on their family(Reference Bisogni, Jastran and Seligson19,Reference Bech-Larsen and Kazbare41) .
For most people, food provides many functions beyond nourishment(Reference Klink, Härtling and Schüz20,Reference Grunert and Meiselman42) . These other functions are sometime integrated into peoples’ interpretations of healthy eating(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Hazley, Stack and Kearney26) . For example, some people see food’s role in promoting well-being and satisfaction as fundamental to living a healthy life(Reference Bisogni, Jastran and Seligson19,Reference Klink, Härtling and Schüz20,Reference Schaefer, Biltekoff and Thomas43) . Under this view, even foods that are seen as ‘unhealthy’ from a nutritional standpoint may be considered ‘healthy’ through their non-nutritive functions(Reference Bisogni, Jastran and Seligson19,Reference Hazley, Stack and Kearney26) . These findings suggest that the healthiness of foods is often context-dependent, as certain ‘unhealthy’ foods can be seen as ‘healthy’ under certain circumstances as they provide benefits to one’s mental well-being(Reference Hazley, Stack and Kearney26,Reference Schaefer, Biltekoff and Thomas43) .
Consumers’ interpretations of sustainable eating
Almost all consumers are familiar with the concept of a healthy diet. Sustainable eating, however, is less well understood. For example, a 2021 survey by the Food Standards Agency (FSA) found that 75 % of UK adults felt they knew what a healthy diet was, whereas only 48 % said they knew what a sustainable diet was(Reference Heard and Bogdan44). Similarly, a recent survey found that only around a third of Irish adults believed they had good knowledge of a sustainable diet(21). These results are consistent with qualitative research conducted in several high-income countries, finding participants often express uncertainty when they are asked to describe a sustainable diet(Reference Hazley, Stack and Kearney26,Reference Hoek, Pearson and James45–Reference van Bussel, Kuijsten and Mars47) . This uncertainty likely explains why consumers perceptions of food sustainability is often inconsistent with scientific evidence.
Van Bussel et al. (Reference van Bussel, Kuijsten and Mars47), recently reviewed the literature examining how adults from high-income countries interpret food sustainability. As with healthy eating, they found that people conceptualise sustainable eating in multiple ways. However, consumers primarily viewed food sustainability from an environmental perspective, with little emphasis on the social or economic aspects of sustainability. To most people, a sustainable diet means eating local and seasonal foods (i.e. reducing ‘food miles’), limiting plastic packaging, eating organic and avoiding food waste(Reference Hazley, Stack and Kearney26,Reference van Bussel, Kuijsten and Mars47) . Some also acknowledge the importance of ethical production methods (e.g. free-range eggs), conserving natural resources, limiting pollution and preventing overfishing(Reference Hazley, Stack and Kearney26,Reference van Bussel, Kuijsten and Mars47) . In contrast, few consumers associated sustainable eating with actual dietary choices, such as limiting red meat consumption(Reference Hazley, Stack and Kearney26,Reference van Bussel, Kuijsten and Mars47) .
Quantitative research further corroborates these qualitative findings. For example, a survey conducted by the FSA found almost half of respondents thought food packaging (47 %) and transportations (46 %) contributed to the environmental impact of food, whereas only 18 % felt the production of meat had an impact(Reference Armstrong, King and Clifford48). Studies consistently find that most consumers are either unaware, or do not believe that meat production has a negative effect on the environment(Reference van Bussel, Kuijsten and Mars47,Reference de Boer and Aiking49) . Although one longitudinal study indicated that Swiss consumers have become more aware of the environmental impact of red meat, most still perceived other factors like eating local food and limiting plastic packaging as having a larger impact(Reference Siegrist, Visschers and Hartmann50).
Reducing plastic packaging and eating seasonally does have some role to play in creating a more sustainable food system. However, consumers overestimate the environmental costs of these action and underestimate the impact of limiting red meat consumption. Hoolohan et al. (Reference Hoolohan, Berners-Lee and McKinstry-West13), estimated that the removal of all packaging and the elimination of hot-housing and air freighting (i.e. a way of modelling more seasonal and local food consumption) would only reduce the GHGe of the average UK diet by 3 % and 5 %, respectively. In contrast, swapping red meat with less carbon-intensive meats like pork or poultry, or cutting out meat entirely was estimated to reduce food-related emissions by 18 % and 35 %, respectively(Reference Hoolohan, Berners-Lee and McKinstry-West13). This is not to say that animal sourced foods have no role to play in a sustainable diet. Moderate amounts of animal products can provide a vital source of nutrition in a healthy and sustainable diet(Reference Beal, Gardner and Herrero51). But current intakes of meat, especially red meat, exceeds planetary boundaries in most high-income countries(Reference Godfray, Aveyard and Garnett52). Thus, improving consumers awareness of the environmental costs of high meat intakes is warranted.
Studies often show that consumers perceive organically produced foods are more environmentally sustainable(Reference van Bussel, Kuijsten and Mars47). While organic production systems do present a clear benefit to the biodiversity of agricultural landscapes(Reference Tuck, Winqvist and Mota53), the evidence for other environmental indicators such as eutrophication, GHGe, land use and acidification potential is less clear. In fact, in many cases, conventionally produced foods have a lower environmental impact(Reference Clark and Tilman54). For instance, Smith et al. (Reference Smith, Kirk and Jones55), modelled the effect of converting all food production in England and Wales to organic and found that despite modest improvements in resource efficiency, the lower yields from organic production led to greater total GHGe. Overall, these findings suggest that most consumers have a poor understanding of the environmental impact of their food choices and often overemphasise the importance of less costly actions (e.g. reducing packaging).
Consumers’ interpretations of healthy and sustainable eating
To date, most studies have examined consumers interpretations of either healthy eating or sustainable eating. Only a few studies have explored how people conceptualise the integration of these concepts (i.e. healthy and sustainable eating)(Reference Hazley, Stack and Kearney26,Reference Hoek, Pearson and James45,Reference Ronto, Saberi and Carins56–Reference Godin and Sahakian58) . A recent survey of Irish adults found that only 12 % of participants thought a healthy diet and a sustainable diet were the same, with around 80 % believing they were ‘similar but different’ (60 %) or ‘not the same’ (20 %) and the remaining 6 % stated that they didn’t know(21). These findings suggests that most consumers believe there are some similarities between a healthy diet and a sustainable diet. However, few consistencies are found when consumers are asked to explain these similarities.
In general, consumers seem receptive to the concept of a healthy and sustainable diet, but few consider this combination in their everyday lives(Reference Hazley, Stack and Kearney26,Reference Hoek, Pearson and James45) . The actions consumers most commonly perceive as benefiting both health and the environment are reducing processed foods and eating organic(Reference Hazley, Stack and Kearney26,Reference Hoek, Pearson and James45) . Interestingly, the perceived environmental impact of processed foods mainly relates to the packaging associated with these products, whereas organic foods are perceived as healthy and environmentally friendly as they are perceived as more natural and free from chemicals or pesticides(Reference Hazley, Stack and Kearney26,Reference Hoek, Pearson and James45) . Overall, consumers seem to have a limited awareness of the commonalities between a healthy diet and a sustainable diet. In a qualitative study of 20 Irish adults, we found few consistencies in the dietary behaviours participants perceived as both healthy and sustainable(Reference Hazley, Stack and Kearney26). For instance, while some thought reducing red meat consumption would be good for their health and the environment, this was not a view shared by most participants. These findings underscore the need to improve consumers awareness of the commonalities between a healthy and sustainable diet.
We also found that participants perceptions of healthy eating were deeply rooted in their personal dietary experiences and self-interested goals (e.g. losing weight)(Reference Hazley, Stack and Kearney26). In contrast, participants perceptions of sustainable eating emerged as abstract dietary ideals, often disconnected from their actual behaviour or food choice motives(Reference Hazley, Stack and Kearney26). This personal disconnect may act as a barrier to embracing environmentally conscious eating habits(Reference Gifford and Chen59). While eating for health is driven by personal motives (e.g. maintaining a healthy weight), sustainable eating is shaped by non-personal motives (e.g. animal welfare)(Reference Van Dam and van Trijp60). As personal motives are more salient to consumers food choices, highlighting the health benefits of sustainable dietary practices may be more appealing than outlining their environmental impacts(Reference Hoek, Malekpour and Raven10,Reference Kenny, Woodside and Perry18) .
Implications for future practice
The evidence presented above highlights several opportunities to foster healthier and more sustainable eating habits. These include enhancing consumers knowledge and understanding of healthy and sustainable diets; overcoming competing priorities and barriers; and creating system-wide changes.
Improving knowledge and understanding
The research presented above suggests that most consumers have a basic understanding of the foods and nutrients that are recommended (e.g. fruits and vegetables) or should be limited (e.g. foods high in fat, sugar and salt) in a healthy diet. However, this basic awareness may not tell the full story. For instance, some studies find that while many can recite dietary recommendations, their ability to determining appropriate portion sizes is less accurate(Reference Huizinga, Carlisle and Cavanaugh61,Reference Rooney, McKinley and Appleton62) . Thus, while education campaigns focused on the specific foods one should eat may be less needed, clearer guidance on appropriate portion sizes may still be warranted. In addition to portion size information, guidance on what terms like ‘balanced’ and ‘moderation’ mean in the context of a healthy and sustainable diet may also be beneficial.
In general, consumers understanding of healthy eating greatly exceeds that of food sustainability. Most consumers overestimate the climate impact of eating local, organic foods and reducing packaging and underestimate the impact of reducing the consumption of red meat. Most consumers are either unaware or do not believe that the production of animal products, especially red meat, has a considerable environmental impact. In fact, the consumption of meat remains a peripheral concern for most Europeans when they considered a sustainable diet(Reference de Boer and Aiking49). Thus, there is a need to build a broader awareness of the carbon footprint of meat, especially red meat, compared to plant-based alternatives.
Beyond providing mere declarative knowledge of what dietary behaviours are considered healthy and sustainable, there is also a need to provide procedural (i.e. how-to) knowledge, so consumers can incorporate these recommendations into their diets. For this reason, practitioners are encouraged to focus on promoting food literacy instead of simply improving awareness of recommendations(Reference Vidgen63). Food literacy refers to the knowledge and skills required to eat a healthy and sustainable diet. This encompasses an awareness of what constitutes a healthy and sustainable diet and the ability to ‘plan, manage, select, prepare and eat foods to meet needs and determine food intake’(Reference Vidgen63). A focus on improving food literacy would aim to equip individuals with the tools they need to make informed choices and adopt healthy, sustainable dietary habits.
While improve consumers knowledge is important, simply providing information may not be enough to change behaviour(Reference Hoek, Malekpour and Raven10). Knowledge is just one of many factors influencing people’s food choices (Fig. 1). For this reason, knowledge is considered a ‘necessary but not sufficient factor’ when it comes to changing eating behaviour(Reference Worsley64). For instance, even when people are made aware of the link between the production of red meat and the climate, few appear open to changing the way they eat(Reference Gillison, Lannon and Verplanken28,Reference Macdiarmid, Douglas and Campbell65) . Other research suggests that the people most interested in receiving information on food sustainability are also those with the most sustainable diets(Reference Edenbrandt and Lagerkvist66). Thus, in addition to improving consumer awareness, strategies are needed to address the broader context in which people make food choices, overcoming competing priorities and barriers.
Overcoming competing priorities and barriers
Foods are rarely selected solely on their health or environmental credentials. Most consumers say they want their food to be produced sustainably. For instance, Heard et al. (Reference Heard and Bogdan44) found that 73 % of UK adults felt it was very (24 %) or fairly (48 %) important to buy food that has a low environmental impact(Reference Heard and Bogdan44). But few consumers will compromise on other factors. In general, people prioritise taste, convenience, price and health over sustainability when making food choices(Reference Kenny, Woodside and Perry18,67) . Thus, there is a need to position healthy and sustainable eating in a way that aligns with other priorities(Reference Gillison, Verplanken and Barnett14).
The way healthy and sustainable eating messages are framed may influence their uptake. For instance, many traditional dietary guidelines promote restraint and restriction which can lead to feelings of guilt when recommendations aren’t achieved(Reference Klink, Härtling and Schüz20,Reference Coveney33) . Instead, practitioner could use pleasure-focused messaging that promotes the sensory and social experiences of healthy and sustainable dietary practices. Several studies have found that pleasure-focused messages are more effective at encouraging healthier eating habits than health-centred approaches(Reference Pettigrew68). Bédard et al. (Reference Bédard, Lamarche and Grégoire34), noted that viewing the enjoyment of eating in terms of sensory satisfaction, mindful eating, memories and social interactions leads to more positive dietary behaviours(Reference Bédard, Lamarche and Grégoire34). These findings support calls for a paradigm shift in health eating promotion, moving away from the ‘food as health’ narrative that emphasises restraint and restriction, to a ‘food as well-being’ perspective that acknowledges the multiple meanings food holds in peoples’ lives(Reference Block, Grier and Childers69).
Few consumers react positively to the idea of eating less meat(Reference Gillison, Lannon and Verplanken28). However, some evidence suggests certain framings may be more positively perceived than others. Hoek et al. (Reference Hoek, Pearson and James45) found participants saw meat-related recommendations as all or nothing, believing it involved the complete elimination of meat, with little attention to how this reduction will be achieved(Reference Hoek, Pearson and James45). This misperception may push consumers further away from meat reduction. Therefore, messages aimed at reducing meat should focus on small behaviour changes, emphasising substitutions that align with the characteristics consumers associate with meat, such as protein. For instance, De Boer et al. (Reference De Boer, Schösler and Aiking70), found consumers were more receptive to meat reduction or substitution strategies that encouraged eating smaller portions of meat, eating more sustainable meat and/ or substituting meat with plant-based proteins, than they were with those emphasising meat free days.
There are several factors inhibiting consumers from transition to a healthy and sustainable diet(Reference Kenny, Woodside and Perry18). Two central barriers are cost and social or cultural norms. Most consumers perceive healthy and sustainable diets as expensive(Reference Kenny, Woodside and Perry18,Reference Zorbas, Palermo and Chung71) . For those living on a low-income, the notion of a climate friendly diet is viewed as a luxury they cannot afford(Reference Verdeau and Monnery-Patris72,Reference Vos, Deforche and Van Kerckhove73) . Modelling research suggests that a healthy and sustainable diet is possible at all income levels with specific target strategies(Reference Reynolds, Horgan and Whybrow74). However, these modelled substitutions only consider the monetary costs associated with dietary change. Daniel(Reference Daniel75), showed that the costs associated with a healthy diet relates to more than just the monetary value of the dietary change. Low-income households also consider the costs of wasted food due to rejection, packaging containing more than needed and foods that are consumed too quickly or are unsatiating(Reference Daniel75). Without appreciating the varied expenses people associated with healthy and sustainable eating, researchers and practitioners may underestimate their true costs. Future initiatives aimed at promoting healthy and sustainable diets should consider the costs of dietary change from the viewpoint of everyday consumers.
Social and cultural norms also play a pivotal role in shaping dietary choices, influencing not only what people eat but also how much they consume(Reference Higgs76). In most high-income countries, like the UK and Ireland, meat is considered an essential component of a meal(Reference Gillison, Lannon and Verplanken28). This social norm makes efforts to reduce meat consumption particularly challenging. Traditional information campaigns are unlikely to shift these deeply ingrained norms. However, strategies informed by behavioural science like altering the choice architecture of peoples’ food environments show promise. For example, Garnett et al. (Reference Garnett, Marteau and Sandbrook77) demonstrated that positioning vegetarian options prominently at the beginning of cafeteria lines can significantly boost the sale of these dishes. These findings suggest that subtle changes in how choices are presented to consumers can have a meaningful impact on promoting healthier and more environmentally friendly eating habits.
Creating system-wide changes
Changing consumers dietary habits will play a pivotal role in the transition to a more sustainable food system. But consumer-oriented actions are just one piece of the puzzle. Improving the health of people and the planet will require system-wide changes. In addition to those aimed at influencing dietary choices, actions are also needed to promote sustainable agricultural practices (e.g. improving fertiliser use efficiency), encourage the reorientation of land use (e.g. providing subsidies to farmers for restoring unproductive farmland to natural habitats, such as rewilding forests), improve the sustainability of aquaculture and wild fisheries (e.g. reducing overfishing) and minimising food loss and waste (e.g. improving cold chain infrastructure)(Reference Hoek, Malekpour and Raven10,Reference Caleffi, Hawkes and Walton11) .
Conclusion
This review highlights how adults in high-income countries hold diverse and multifaceted meanings for healthy eating and sustainable eating. While many consumers have a reasonable awareness of what constitutes a healthy diet, their interpretations extend beyond traditional dietary guidance, often incorporating other aspects of eating, such as enjoyment and socialisation. In contrast, most consumers have a limited understanding of food sustainability. Most view sustainable diets through an environmental lens, often overemphasising the importance of eating local, organic food and reducing packaging, while underestimating the impact of reducing red meat consumption. Moreover, although consumers seem open to the idea of a healthy and sustainable diet, this remains a novel concept for many. This disparity in understanding presents an opportunity to enhance public awareness of healthy and sustainable diets. However, knowledge alone is insufficient to drive behavioural change. Future campaigns should also address consumers’ competing dietary priorities and advocate for system-wide changes to promote a healthier and more sustainable food system.
Acknowledgements
The authors would like to thank the Nutrition Society for the opportunity to present this work as part of the Postgraduate Symposium of the Irish Section Conference 2023 and for the opportunity to publish a review in the Proceedings of the Nutrition Society.
Financial support
This work was supported by funding from the Irish Department of Agriculture, Food and the Marine (DAFM National Funding Call 2019).
Conflict of interests
The authors declare no conflicts of interest.
Authorship
D.H. conducted the literature review and wrote the first draft of the manuscript. J.M.K. provided expert advice throughout the literature review process. Both authors critically reviewed the manuscript and approved the final version submitted for publication.
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