National dietary guidelines generally recommend a reduction in fat and red meat consumption and an increase in carbohydrate consumption to promote good health [1
]. These recommendations have been based on theoretical links between fat consumption and coronary heart disease risk [3
], and associations between red and processed meat consumption and incidence of cardiovascular disease and certain types of cancer [4
]. Despite these recommendations, diet-related morbidity as well as cardiovascular disease, diabetes, and obesity and overweight, have risen markedly, while fat and red meat consumption has declined and carbohydrate consumption has increased [5
]. In parallel, a substantial body of evidence has emerged linking high carbohydrate consumption, particularly dietary sugars, to increased risk of chronic conditions including metabolic syndrome, obesity, diabetes, and related chronic illnesses [7
]. Other research claims that the relations between red (including processed) meat consumption and increased risk of chronic disease are based on low-quality evidence [8
]; and that meat consumption provides a plethora of health benefits [9
Against this backdrop of inconsistent evidence and ongoing debates on the harms and benefits of animal-sourced food and fat consumption [11
], some populations have been reducing their carbohydrate consumption for health reasons, leading to the popularity of low-carbohydrate and ketogenic-type diets [12
]. There is debate over the health benefits and risks of low-carbohydrate and ketogenic diets. Some evidence argues against these diets, putting forth short-term (e.g., constipation, headache, halitosis, muscle cramps, bloating, diarrhea) and long-term (e.g., decreased bone mineral density, nephrolithiasis, cardiomyopathy, anemia, and neuropathy of the optic nerve) health concerns [13
]. However, following a carbohydrate restricted dies has also been linked to adaptive health outcomes, such as sustained weight loss, improved physique, reduced hunger, improved mood and cognition, better digestion, improved biomarkers, and higher quality of life [15
]. In addition, a growing number of case reports suggest that carbohydrate-restrictive diets consisting almost exclusively of animal-sourced foods are effective in managing and even reversing chronic health conditions, including obesity, type 1 and 2 diabetes, Crohn’s disease, and epilepsy [17
]. The underlying physiological mechanism hypothesized to explain the health-related benefits of carbohydrate reduction is nutritional ketosis [18
]. Furthermore, the avoidance of plant antinutrients, such as phytates, lectins, oxalates, and fiber, has also been proposed as a factor explaining health benefits experienced through carbohydrate restriction [19
]. The lack of consensus on the health benefits and risks of carbohydrate reduction could be explained, at least in part, by the absence of a singular low-carbohydrate diet [20
]. Many types of low-carbohydrate and ketogenic-type diets appear in the published literature and in real-life, with variable adherence patterns, which hinders efforts to reach overarching conclusions on the health-related consequences of the diets.
Similarly, there are numerous versions of diets that severely limit or entirely exclude carbohydrate intake, colloquially labeled zero-carb diets. People eating zero-carb diets are known to consume, almost exclusively, animal-sourced foods (i.e., all types of meats and fish, eggs, and dairy), at the expense of plant-based foods (i.e., fruits, vegetables, legumes, and grains). These diets may have emerged in response to calls for “personalized” approaches to nutrition [21
]. The prominence of the internet as a primary venue of health-related information and social interaction has also likely facilitated the emergence of zero-carb diets. There are many long-established virtual zero-carb communities with large followings. For example, the zero-carb subreddit was created in 2010 and currently counts 114,000 registered members (see https://www.reddit.com/r/zerocarb/
, accessed on 13 April 2019). However, there has been, to date, no published empirical research on the factors that influence people to take up, and remain committed to, a zero-carb diet [22
]. There is also no empirical research on the shared definitions and features of a zero-carb diet among those who follow them, which is important in order to document typical practices, and inform research on potential health benefits and risks. The rise in popularity of zero-carb diets in media outlets has created the substantive need for information for those already following these diets and those interested in taking up the diet in the future. Furthermore, the need for research in this area is important given the increasing evidence that carbohydrate-restrictive diets have beneficial health effects. The absence of research on zero-carb diets has also presented challenges to health-care professionals (e.g., physicians, nutritionists, psychologists) interested in establishing the factors that determine the diet uptake, and provide appropriate support for people following these types of diet.
The current study aimed to fill this evidence gap by exploring the beliefs and experiences of adults on zero-carb diets. Specifically, we aimed to identify the shared knowledge and understanding of what characterizes a zero-carb diet and to identify the sets of beliefs that underpin decisions to begin and maintain a zero-carb diet. Given the dearth of empirical research on zero-carb diets, we used a qualitative survey to gain insight into the beliefs and experiences of those eating zero-carb diets. Online surveys have been gaining traction as a qualitative research method to provide in-depth information on beliefs and behaviors [23
]. The method offers numerous advantages for researchers, such as a “wide-angle lens” approach on the topic under investigation that allows the collection of diverse views, perspectives, and experiences of geographically dispersed populations; the elicitation of “within-group” views from marginalized and/or overlooked populations; heterogeneity, instead of typicality of views, when larger samples are recruited; and the quick collection of large data sets. The method also offers some advantages over traditional interview approaches by providing anonymity for respondents and greater control over when, where, and how they express their views, without feeling influenced or led by an interviewer or facilitator. For an overview of the online survey method, see Braun, Clarke, Boulton, Davey, and McEvoy [24
The present study explored the beliefs and experiences of people eating a zero-carb diet for a minimum of six months using an online qualitative survey method distributed via Twitter, a social media platform. Participants were asked to describe and elaborate on the advantages, disadvantages, normative influences, facilitators, and detractors of eating a zero-carb diet. Data were thematically analyzed. Themes presented participants’ shared understanding and definition of the diet, as well as their experiences with the diet.
4.1. Zero-Carb Diet: Definition and Wellbeing
A basic definition of a zero-carb diet emerged based on participants’ shared dietary habits. According to participants, a zero-carb diet involves the consumption of a variety of foods that are predominately, but not exclusively, animal-sourced. The types and amounts of foods consumed, as well as the timing of the meals, were idiosyncratic. “One”, singular, zero-carb diet did not emerge, and therefore, the term “zero-carb diet” does not refer to a specific, clearly-bound set of foods, macronutrient ratios, or the complete elimination of carbohydrates. While the label zero-carb diet is empirically imprecise, it is an appropriate descriptor for the diet because it captures participants’ shared understanding of the development and evolution of their dietary practices, their goal to reduce carbohydrate intake to a bare minimum, and the psychophysical changes resulting from carb restriction/exclusion. For example, many participants in the current study described a process of gradual carbohydrate reduction, originating from paleo, low-carb, or ketogenic eating styles. This suggests a continuum of carbohydrate restrictive diets, with zero-carb variants located at the extreme end of the continuum. Participants reported that they arrived at a zero-carb variant that suited them and gave them the most health benefits, through personal study, food experimentation, and interaction with like-minded people. In the present study participants also reported experiencing a wide variety of wellbeing benefits that they attributed to their diet, including better digestion, better metabolic health biomarkers, better physique, vitality, reduced hunger, improved mood, joy, knowledge-gaining, personal development and experimentation, and social relationship development. Furthermore, a notable finding from the current data is that a zero-carb diet also seemed to covary or facilitate other health-promoting strategies, including fasting and exercising. Taken together, the data from the current research provide important information on the label of this particular variant of a low-carbohydrate diet, the types of expected eating patterns shared by those following the diet, and insight into the ways individuals adopt and refine their dietary practices while following the diet.
The zero-carb diet introduced challenges to participants’ lives. Some of the challenges were relatively innocuous daily hassles, such as eating out and grocery shopping challenges, and boredom due to limited food types consumed. Other challenges were more serious, with potentially negative health implications, such as experiencing or expecting to experience stigma, strife in interpersonal relationships, lack of guidance and support from healthcare providers, adverse physiological symptoms, and worry about the long-term healthfulness of the diet. Nevertheless, participants framed challenges as transient or not significant enough to derail maintaining their diet. If anything, overcoming these challenges appeared to bolster participants’ resolve in adhering to the diet. All but one participant reported intentions to follow the diet indefinitely, and most reported that others’ disapproval of the diet did not matter enough to stop them. Participants largely overcame challenges through personal research and experimentation with foods and closely interacting with online communities, often described as families. These findings are congruent with other research on individuals following carbohydrate-restrictive diets, where participants reported a strong desire to continue with the diet, despite similar challenges [37
]. It appears that a strong group identity based on adherence to so-called unconventional diets helps to override or negate challenges, through bonding among group members over shared values, goals, and outcomes of the diet. Comparable experiences have been reported by individuals following vegetarian and vegan diets, with a substantive body of research documenting strong, cohesive social identities among individuals identifying as vegetarian and vegan [39
]. By contrast, research into the social identities of those following carbohydrate-restrictive diets is scarce, although there are some preliminary studies [37
]. While the present study did not specifically set out to identify a zero-carb identity, a key emergent finding from our data suggests that such an identity appears to exist.
4.3. Implications for Research and Practice
Based on the present findings, we recommend additional research in several domains. First, we recommend research into the safety and efficacy of excluding or severely limiting carbohydrates for extended periods of time. Our data indicate that people eating zero-carb diets for at least six months experience important benefits but also shortcomings, all of which warrant further investigation, especially through clinical trials. In addition, it would be important to account for changes in beliefs, motives, and perspectives on zero-carb diets in the participants of these trials. This will provide important data on how the efficacy and experience of change affect individuals’ beliefs, such as those identified in the current study.
Based on the current data, we note that people eating zero-carb diets are unlikely to receive support and care from conventionally trained health professionals, who have not received specific training on these dietary practices or have insufficient background information on the health and social implications of carbohydrate restriction. We also note that people eating zero-carb diets experience stigma from those around them that are unfamiliar with this pattern of eating, including healthcare providers. Prior evidence overwhelmingly suggests that experience—and even the anticipation—of stigma is a major barrier to seeking and receiving healthcare and quality of life [43
]. Consequently, participants in the present study sought and depended on sources of information and support outside their regular healthcare providers, typically from online zero-carb communities. While many in these communities may have appropriate backgrounds and knowledge of the diet, there is also a risk that people may receive information that lacks an evidence base or credibility. Lack of support and stigma by healthcare providers has also been documented among people following other types of carbohydrate-restrictive diets [38
]. It is also documented that healthcare providers who support, or express intention to support, those on carbohydrate-restrictive diets experience stigma themselves by their colleagues [46
], reflecting a relative lack of acceptance and knowledge among the mainstream healthcare community. Given participants’ expressed strong motives to adhere to the diet, with or without healthcare provider support, we suggest that healthcare providers seek to keep informed and upskill themselves to support this population. Related, we advocate research into how healthcare provider stigma can be reduced and how healthcare providers can support and monitor people on these diets.
We also recommend research into the formation of social identities emerging from carbohydrate restriction. It is well established that food choices are a means to express personal values, beliefs, and worldviews [37
]. Our findings suggest that a zero-carb social identity exists. These findings are consistent with social identity theory [47
], which suggests that people develop social identities based on the shared beliefs and attitudes of the social groups to which they belong (ingroups) and that such identities are a source of motivation and self-esteem. Our participants shared values, beliefs, and practices; belonged to groups based on their food choices and viewed these ingroups favorably. Although carbohydrate-restrictive diets have a long history, with formalized (medical) supervised plans appearing in the early 1920s [48
], the shared identity of people following these types of diets has been largely overlooked, but limited data exist [37
]. Future intervention research, therefore, may seek to capitalize on such social identities as a means to promote adoption and maintenance of zero-carb diets among those interested in, and receptive to, adopting a zero-carb diet. Numerous behavior change strategies have that tap into such identities have been identified and these may inform the development of the content of such interventions [49
] (pp. 649–660, 225–236).
Finally, we recommend research into how people following zero-carb diets, and other carbohydrate-restrictive diets, maintain their diets in face of challenges presented in the modern dietary landscape. One of the consistent barriers discussed by participants in the current study was the high availability of high-carb foods and beverages, and the relative lack of low-carb or zero-carb alternatives. Participants, like most people in Western nations, are consistently being marketed foods high in carbohydrates and sugars. Participants felt acutely that they were going against societal norms in their efforts to exclude carbohydrates, experiencing derision and stigma as a result. Exploring how those on zero-carb, and other carbohydrate-restrictive diets, navigate through and resist environments where there is high availability of high-carbohydrate and high-sugar foods, can inform the development of strategies promoting consumption of alternatives to such foods. Given the well-documented link between high carbohydrate consumption and metabolic health conditions like type 2 diabetes and obesity, such an approach is likely to have broad implications for health.
4.4. Strengths and Limitations
The present study was the first to explore beliefs and experiences of people eating zero-carb diets and to elicit a definition of a zero-carb diet, filling an evidence gap. Other strengths of the study included the adoption of fit-for-purpose and novel qualitative methods and recruitment of a large, international sample of people who had been voluntarily on a zero-carb diet for at least six months, with a high completion rate. The use of the online qualitative survey method afforded additional advantages including a “wide-angle lens” approach to encompass diverse views and experiences of participants; the elicitation of “within-group” views from hard-to-reach populations; heterogeneity in views by covering a larger cross-section of the population of interest; participant anonymity and control over the location and time of participation by participants; and the minimization of interviewer demand characteristics. Furthermore, our procedure has clear reproducible steps allowing others to replicate the approach.
In addition, the study was developed based on established study quality criteria [27
], extant frameworks of online qualitative survey methodology [23
], and analyses were appraised against Braun and Clarke’s [33
] criteria for high-quality thematic analysis. Finally, for the purposes of maintaining trustworthiness and transparency of our data, we stated the first author’s personal experimentation with a zero-carb diet and provided all study materials, data files, and data analyses in the Supplementary Materials online
These strengths notwithstanding, current findings should be interpreted in light of some limitations. A potential limitation is participants’ self-selection bias. Participants volunteered their participation and were likely those with high involvement and immersion in the diet and high motivation to continue with the diet. Consequently, their views may differ from others on a zero-carb diet who did not elect to participate, and those who were not reached through our recruitment strategy. A related limitation is that our recruitment and sampling method did not allow us to estimate response rates, and, therefore, we could not ascertain refusal rates, which may have provided an indication of the extent of self-selection. Although a random stratified sample is highly desirable as it enables better generalization of findings to the broader population, the current sample comprised participants with highly-specialized interests and behaviors for which no clear norms exist making it challenging to recruit a sample that is representative of all followers of low-carb dieters. In addition, although we recruited a large sample from multiple backgrounds and national groups, most participants were of high socioeconomic status (Table 1
). This places limits on the extent to which current findings can be generalized to all individuals following zero-carb diets. Future research should consider pro-active recruitment strategies that reach zero-carb dieters who do not engage with social media and those who do not tend to respond to unsolicited requests for participation.
4.5. Reflexive Analysis
We aimed to collect and analyze and present participants’ perspectives and experiences with a zero-carb diet fairly and disinterestedly, but we acknowledge that we, as researchers play a role in constructing knowledge, so we were mindful to be reflexive throughout the course of the research. The first author is an applied health psychologist with an interest in human nutrition, experience in mixed-methods psychological research, and extended experience with eating a zero-carb diet. The second author is an applied biological scientist, with expertise in interdisciplinary research relating to human and animal health and wellbeing; they have no experience with a zero-carb diet. The third author is an applied health and social psychologist with experience in mixed-methods psychological research; they have no experience with a zero-carb diet. The research we have produced likely benefits from pooling expertise from different academic backgrounds; an insider approach to a zero-carb diet, and an approach based on an empirical understanding of zero-carb eating.