Original Article | Published:

Consumers' readiness to eat a plant-based diet

European Journal of Clinical Nutrition volume 60, pages 342351 (2006) | Download Citation

Guarantor: EJ Lea.

Contributors: EJL collected and analysed the data. DC and AW assisted with design of the questionnaire. All authors contributed to the data analysis and interpretation and to the preparation of the manuscript.

Subjects

Abstract

Objective:

The aim of this study was to examine consumers' readiness to change to a plant-based diet.

Design:

Mail survey that included questions on readiness to change, eating habits and perceived benefits and barriers to the consumption of a plant-based diet.

Setting:

Victoria, Australia.

Subjects:

A total of 415 randomly selected adults.

Results:

In terms of their readiness to eat a plant-based diet, the majority (58%) of participants were in the precontemplation stage of change, while 14% were in contemplation/preparation, and 28% in action/maintenance. Those in the action/maintenance stage ate more fruit, vegetables, nuts, seeds, whole-meal bread, and cooked cereals than those in earlier stages. There were statistically significant differences in age and vegetarian status between the stages of change, but not for other demographic variables. There were strong differences across the stages of change with regard to perceived benefits and barriers to plant-based diets. For example, those in action/maintenance scored highest for benefit factors associated with well-being, weight, health, convenience and finances, whereas those in the precontemplation stage did not recognise such benefits.

Conclusions:

These findings can be utilised to help provide appropriate nutrition education and advertising, targeted at specific stages of change. For example, education about how it is possible to obtain iron and protein from a plant-based diet and on the benefits of change, in addition to tips on how to make a gradual, easy transition to a plant-based diet, could help progress precontemplators to later stages.

Sponsorship:

Australian Research Council.

Introduction

A plant-based diet may be defined as an eating pattern that is dominated by fresh or minimally processed plant foods and decreased consumption of meat, eggs and dairy products. It involves increased consumption of a variety of grains (including whole grains), fruits, vegetables, legumes, nuts and seeds, in comparison to a meat-centred diet. Diets that emphasise a greater consumption of plant foods are increasingly being recognised by health authorities as providing important health benefits, including decreased disease risk such as heart disease, various cancers and type 2 diabetes (World Cancer Research Fund and American Institute for Cancer Research, 1997; Potter, 2000; Bazzano et al., 2002; American Dietetic Association, 2003; Key et al., 2003; Montonen et al., 2003). Despite these health benefits, consumption of plant foods in many developed countries, including Australia, does not meet recommended levels (Stables et al., 2002; Lang et al., 2003; Victorian Government Department of Human Services, 2004). However, although consumption of a range of individual plant foods has been measured (Hunt et al., 2000; Agudo et al., 2002; Stables et al., 2002; Lang et al., 2003), to our knowledge there has been no examination of that section of the population who are eating a plant-based diet, including their social and cognitive characteristics.

Worldwide, there are a variety of programmes to encourage increased consumption of plant foods, particularly fruits and vegetables. These include the 5 A Day for Better Health programme in the USA, the UK Department of Health's 5 A DAY program, the Coles Supermarkets/Dietitians Association of Australia 7-a-day Programme, and the proposed World Health Organization initiative to promote fruit and vegetables (Stables et al., 2002; World Health Organization, 2003). A variety of strategies have been used to promote increased consumption of plant foods. For example, some focus on individuals, such as changing their beliefs and knowledge (Ammerman et al., 2002), while others attempt to alter the environment (e.g. increased availability of plant foods) (Glanz and Hoelscher, 2004; Glanz and Yaroch, 2004). Basing such strategies on theoretical behavioural models, such as the stages of change (transtheoretical) model of behavioural change, can increase their effectiveness (Ammerman et al., 2002).

The stages of change model is a useful means by which to segment the population according to whether they are consuming a plant-based diet or not. The stages of change model posits behavioural change occurring through five separate stages: (1) precontemplation; (2) contemplation; (3) preparation; (4) action; and (5) maintenance (Prochaska et al., 1992, 1994). Precontemplation is the stage when individuals have not considered changing their behaviours. Contemplation is the stage when individuals are thinking about changing their behaviours. The preparation stage is reached when individuals intend to change their behaviours in the next month. According to the Prochaska et al. (1992, 1994) schema, at the action stage, the behaviour change has been made in the last 6 months, while maintenance is the stage when the behaviour change has been adopted for six months or more. However, it has been argued by Povey et al. (1999) that these time frames are somewhat artificial when applied to dietary behaviours, as their study found that people making or maintaining a dietary change had done so for a range of time periods. The stages of change model may ultimately help in the design and implementation of effective strategies to improve the likelihood of dietary change, such as by tailoring communications to suit people at various stages. Indeed, it has provided a number of insights into the cognition states that occur when people make dietary changes to eat healthier and lower-fat foods (de Graaf et al., 1997; Ôunpuu et al., 2000) and to willingness to meet grain, fruit and vegetable guidelines (Ling and Horwath, 2000; Van Duyn et al., 2001; Horacek et al., 2002; Greene et al., 2003). Programmes based on stages of change for dietary fat and fruit and vegetable intake have been found to be successful (Finckenor and Byrd-Bredbenner, 2000; Campbell et al., 2001).

In particular, stages of change appear to be associated with the perceived benefits and barriers, or decisional balance, of dietary change (Ôunpuu et al., 2000; Van Duyn et al., 2001; Ma et al., 2002). The benefits of change need to outweigh the barriers for behavioural change to occur (Rosenstock, 1974; Wolinsky, 1980; McIntosh et al., 1996; Nestle et al., 1998). Perceived benefits of healthy eating and dietary change include weight control, being healthy, improved quality of life and disease prevention (Zunft et al., 1997). Barriers to dietary change include irregular working hours and the belief that one's diet is already healthy (Beard et al., 1989; Lloyd et al., 1995; Kearney et al., 1997; Lappalainen et al., 1997; Cox et al., 1998; Stubenitsky and Mela, 2000). Perceived barriers to eating a plant-based diet have been found to include lack of information, while benefits include health benefits such as decreased saturated fat intake (Lea et al., 2005a). Precontemplators have been found to perceive more barriers than benefits for fruit and vegetable consumption, in contrast to those in preparation, action and maintenance (Ma et al., 2002). It is likely that there would also be differences in perceived barriers and benefits between individuals in various stages of change with regard to plant-based diets.

Previous research has shown that demographic variables such as sex and age are related to health care and food beliefs and behaviours (Van Duyn et al., 1998; Fraser et al., 2000; Kearney et al., 2000; Wardle and Steptoe, 2003; Worsley et al., 2003; Lea and Worsley, 2004). For example, females, older people and those with a higher level of education are more likely to attempt to eat more healthily (Kearney et al., 2000). Therefore, there may also be sociodemographic differences between stages of change with regard to plant-based diets. That is, members of different sociodemographic groups may hold different attitudes, beliefs and arguments according to their experiences.

The aim of this study was to examine the readiness to change to a plant-based diet among a sample of Australians. It was hypothesised that consumption of plant and animal foods would vary according to stages of change, with those at more advanced stages consuming plant foods more often and animal foods such as red meat less often than those at earlier stages. Differences in sociodemographic variables, such as age, sex and education, according to stages of change were also assessed. Finally, differences in a range of perceived barriers and benefits of eating a plant-based diet between those at various stages of change were examined. The information provided will allow the implementation of communication and other strategies to increase consumption of plant foods and the prevalence of plant-based diets, with the ultimate goal of improving population health.

Methods

Procedure

In all, 1000 people were randomly selected from the Victorian population by using the software package Australia on Disc (May 2003 version, Dependable Database Data Pty Ltd), containing a comprehensive list of residences from the telephone directory.

A questionnaire, cover letter and reply-paid envelope were mailed to each individual in February 2004, with questionnaire design and administration based on Dillman's (2000) recommended methods. The questionnaire mail out was preceded by a letter informing each person that a questionnaire would be delivered in the following few days. A number of follow-ups to the original mailing were conducted to improve the response rate. A reminder postcard was posted 1 week after the questionnaire. This was followed 5 weeks later by a replacement questionnaire posted to nonrespondents. After a further 4 weeks, at least two attempts were made to reach nonrespondents through telephone. Finally, a replacement questionnaire was sent by registered post to a small random selection of those who were unable to be contacted, in order to establish whether they were still residing at that address.

The questionnaire

The questionnaire consisted of eight pages of questions and a cover sheet. Placed prominently on the cover sheet was a definition of plant-based diets: ‘An eating pattern dominated by fresh or minimally processed plant foods and decreased consumption of meat, eggs and dairy products. Compared to meat-centred diets, it involves increased consumption of a variety of grains (including whole grains), fruits, vegetables, legumes, nuts and seeds. This does not necessarily mean a vegetarian diet.' There was no specification of the quantity of each food that should be consumed, in recognition of the potential for variation in a plant-based diet and due to the lack of such a definition in the literature. Examples of plant foods and plant-based foods and meals were provided, such as ‘grains – wheat, rice, oats, barley’, ‘lentil soup’, ‘pasta’, ‘baked beans’, and ‘vegetable and almond stir fry topped with a small amount of chicken or tofu served with rice’.

Table 2: Means and s.d.'s for frequency of consumption of food items for stages of change groups (precontemplation, contemplation/preparation, action/maintenance), together with P-values from analysis of variance for comparisons between groups
Table 3: Results of principal components analysis of the benefits of eating a plant-based diet
Table 4: Results of principal components analysis of the barriers towards eating a plant-based diet

The questionnaire was devised from a literature review (Schwartz, 1992; Cox et al., 1998; Kearney and McElhone, 1999; Povey et al., 1999; Marks et al., 2001; Rutishauser et al., 2001; Ma et al., 2002; Lea and Worsley, 2003a, 2003b), and the findings of 10 consumer focus groups about plant foods (Lea et al., 2005b). The main sections of the questionnaire that are relevant to this paper are:

  1. Stage of change (five items), including ‘Are you currently eating a plant-based diet?’, ‘Are you thinking about eating a plant-based diet in the future?’ and ‘Have you decided to eat a plant-based diet in the future?’ These items were adapted from Povey et al. (1999). Response options were no, yes and, for the latter two items, I am already eating a plant-based diet. Those who indicated in the first item that they were currently eating a plant-based diet were asked for the length of time in months and/or years they had eaten such a diet.

  2. Current eating habits (15 items), including a range of foods of both plant and animal origin. Several of the items were adapted from the work of Marks et al. (2001). The number of serves of vegetables and fruit consumed daily were measured by the following items: ‘How many serves of vegetables do you usually eat each day, not counting potato chips, wedges, fries or crisps? (a serve=1/2 cup cooked vegetables or 1 cup of salad vegetables)’ and ‘How many serves of fruit do you usually eat each day, not counting fruit juice? (a serve=1 medium piece of fruit such as an apple or 2 small pieces such as plums or 1 cup of diced pieces or 4–6 pieces of dried fruit – count only one serve per day of dried fruit, even if you eat more)’. The remaining 13 items measured frequency of consumption of a variety of foods, with the question: ‘How often do you eat the following foods?’. Foods included nuts, cooked cereals (e.g. pasta), red meat, fruit juice and legumes (listed in Table 2). Response options were never/rarely, 1–3 times a month, 1–4 times a week, daily/almost daily and 2+ times per day.

  3. Perceived barriers to eating a plant-based diet (27 items), including ‘I don't know how to prepare plant-based meals’ and ‘I would have to go food shopping too often’ (Table 4). Items were derived from the results of consumer focus groups on plant foods and plant-based diets (Lea et al., 2005b) and from the literature on consumer beliefs about plant foods, vegetarian diets and healthy eating (e.g. Cox et al., 1998; Kearney and McElhone, 1999; Lea and Worsley, 2003a, 2003b). Response options ranged between strongly disagree and strongly agree on a five-point scale.

  4. Perceived benefits of eating a plant-based diet (24 items), including ‘Decrease my saturated fat intake’ and ‘Save money’ (Table 3). Items were derived from the same sources as those for perceived barrier items (above). Response options ranged between strongly disagree and strongly agree on a five-point scale.

  5. Sociodemographic information (14 items), including sex, age, highest education level and self-identified vegetarian status (no, yes and semi-vegetarian). No definitions of ‘vegetarian’ or ‘semivegetarian’ were provided.

Data analysis

All analyses were conducted with SPSS for Windows statistical software (version 11.5). Respondents were placed into stages of change with regard to consumption of a plant-based diet, with the staging algorithm adapted from Povey et al. (1999) algorithm for dietary behaviours. If they indicated that they were not thinking about eating a plant-based diet in the future and had not decided to eat such a diet, they were classified in the precontemplation stage. If they were thinking about eating a plant-based diet in the future but had not decided to eat one in the future, they were included in the contemplation stage. Those who were thinking about eating a plant-based diet and had decided to eat one were considered to be in the preparation stage. Those in the action stage were those who stated that they were currently eating a plant-based diet. This was also the case for those in the maintenance stage, with the added proviso that they had been eating a plant-based diet for at least 6 months (Prochaska et al., 1992, 1994). Given the small number of respondents who were in the action stage (n=7), the action and maintenance stages were combined for analysis purposes. Similarly, in order to provide adequate numbers for statistical analysis, the contemplation and preparation stages were combined (n=21 and 35, respectively). Thus, the three stages of change categories used in subsequent analyses were precontemplation, contemplation/preparation and action/maintenance.

The consumption of plant and animal foods according to stages of change was assessed by comparing means and using analysis of variance to identify the level of statistical significance. Post hoc pairwise multiple comparisons (Fisher's LSD test) were performed to identify which pairs of means were different. Thus, the mean number of serves of vegetables and of fruit eaten per day was compared between stages of change groups. In order to increase comprehension of the mean frequency of consumption of the remaining food items and to improve comparability with the fruit and vegetable items, the response categories were recoded to reflect the number of times each food was eaten per day. Therefore, never/rarely was recoded to 0.01, 1–3 times a month to 0.07, 1–4 times a week to 0.36, daily/almost daily to 1 and 2+ times per day to 2. Given the low n in a number of categories for some items, even after reduction of the five frequency of consumption response categories to two or three, comparing the mean was more statistically viable than comparing prevalence using χ2 tests.

Differences in sociodemographic variables according to stages of change were also assessed. Crosstabulations, including Pearson's χ2 test of statistical significance, were used for sex and vegetarian status (self-defined vegetarian, nonvegetarian or semivegetarian), while means and analysis of variance were used for education, age and household income.

Differences in perceived barriers and benefits of consumption of a plant-based diet according to stage of change were examined. In order to do this, factor analysis (principal components analysis with varimax rotation) was performed on each of the belief sections. Principal components analysis is a multivariate statistical technique that can be utilised to examine the underlying relationships between a number of variables and to summarise the variables into a smaller set of components or factors (Hair et al., 1995). Data reduction can be achieved by substituting factor scores, or composite measures for each factor, for the original variables. The means of the resulting factor scores were compared between each of the stages of change groups and analysis of variance was used to identify level of statistical significance. Post hoc pairwise multiple comparisons (Fisher's LSD test) were performed to identify which pairs of mean factor scores were different.

Results

The response rate was 51% (n=415), after taking into account those who could not be contacted. A fifth of the sampling frame (n=187) were not able to be contacted because their addresses were incomplete or had changed since the sampling frame was compiled, or were deceased, or were unable to be contacted by telephone.

The sociodemographic characteristics of the respondents and the general Victorian population, as obtained from the 2001 Census (Australian Bureau of Statistics, 2002), are listed in Table 1. Compared with the Census data, the main biases were over-representation of women, those aged 45 years and over and those with a nonschool qualification.

Table 1: The demographic characteristics of the random population survey respondents (n=415) compared with the Victorian population as a whole, as obtained from the 2001 Census

Over half of the respondents (58%, n=227) were classified as being in the precontemplation stage. In all, 5% (n=21) were classified as contemplators and 9% (n=35) as in the preparation stage, giving a total of 14% (n=56) in the combined contemplation/preparation stage. Very few were in the action stage (2%, n=7), while over a quarter were in the maintenance stage (27%, n=105), giving a total of 28% (n=112) in the combined action/maintenance stage. A number of respondents (n=20) were unable to be classified.

There were statistically significant differences between stages of change groups for a number of food items (Table 2). Those in action/maintenance ate more serves of fruit and vegetables each day and ate nuts, seeds, whole-meal bread and cooked cereals more often than those in the other stages. It should be noted that vegetable consumption was low even for those in action/maintenance, with the mean number of serves being only 2.8±1.8/day for this group, although fruit consumption was adequate (2.6±1.5 serves). The action/maintenance group ate white bread and red and white meat the least often, with those in precontemplation eating these foods most frequently. Dairy products were eaten most frequently by those in precontemplation, with those in contemplation/preparation eating them least often. There were no statistically significant differences between stages for legumes, fruit juice, breakfast cereals, fish/seafood and eggs.

There were no statistically significant sex, household income or education differences between stages of change groups. However, there were age and vegetarian status differences (data not tabulated). Age differences were not linear and therefore difficult to interpret, with the main difference being that those in the contemplation/preparation were younger than those in the other two groups (mean of 47±13 years for contemplation/preparation compared to 53±15 years for the remaining two groups, P<0.05). The strongest differences were with regard to vegetarian status (P<0.001), with those in the action/maintenance group being more likely to be semivegetarian or vegetarian than those in the other two groups. Over a fifth in this group considered themselves to be semivegetarian (22, 18 and 5% for action/maintenance, contemplation/preparation and precontemplation, respectively). There were only three vegetarian respondents, all of whom were classified in the action/maintenance group.

Four components with eigenvalues greater than unity were derived from principal components analysis of the benefit items, accounting for 60% of the variance. The factors are listed in Table 3 and were provisionally labelled: Well-being benefits, Weight and health benefits, Ethical benefits, and Convenience and financial benefits. Measures of internal consistency (Cronbach's α) for items with a loading of 35 or over indicated that all of the factors had high internal consistency.

Five components were derived from principal components analysis of the barrier items, which accounted for 59% of the correlation matrix (Table 4). These were provisionally labelled: Personal barriers, Family and convenience barriers, Health barriers, ‘Junk’ food, shopping, eating out and financial barriers, and Information barriers. All five factors had high internal consistency.

Comparisons between mean benefit factor scores and stages of change showed statistically significant differences for all four factors (Table 5). Those in action/maintenance scored highest and those in precontemplation the lowest on all factors except Ethical benefits, for which the contemplation/preparation group scored highest. However, post hoc pairwise comparisons found that the mean score for Ethical benefits was not significantly different between contemplation/preparation and action/maintenance.

Table 5: Means and s.d.'s for benefits and barriers of consumption of a plant-based diet factor scores for stages of change groups (precontemplation, contemplation/preparation, action/maintenance), together with P-values from analysis of variance for comparisons between groups

Comparisons between the means of the barrier factor scores and stages of change found statistically significant differences present for all of the factors (Table 5). Those in precontemplation scored highest for Family and convenience barriers and Health barriers, with those in action/maintenance the lowest. They also scored the highest for Personal barriers, although in this case contemplation/preparation rather than action/maintenance scored the lowest. The contemplation/preparation group scored highest for ‘Junk’ food, shopping, eating out and financial barriers and Information barriers, with action/maintenance the lowest.

The post hoc pairwise comparisons did not find three distinct stages of change (Tables 2 and 5). Where statistically significant differences were present, they tended to be between the first two stages (i.e. precontemplation, contemplation/preparation) and the final stage (action/maintenance), between the first stage and the final two stages, or between the first and final stage. The only factor or item where a statistically significant difference was found between each stage was Information barriers.

Discussion

This is the first study that has been conducted on plant-based diets and stages of change, and thus may be considered exploratory. This study suggests that a large proportion of the population is not yet ready to consume a plant-based diet, with over half of the participants classified as being in the precontemplation stage. Over a quarter were in the maintenance stage, with very few being in action. The remainder were in contemplation or preparation. Previous research on stages of change for related eating behaviours (healthy eating, low-fat diets, and fruit, vegetable and grain consumption) has generally found fewer people to be in precontemplation and more to be in maintenance than was found here (Povey et al., 1999; Ôunpuu et al., 2000; Van Duyn et al., 2001; Ma et al., 2002; Greene et al., 2003). This may partly be due to the focus on the total diet, rather than specific aspects of the diet, such as vegetables or low fat. Eating a plant-based diet is presumably viewed as being more difficult to achieve, or, alternatively, as less desirable to achieve. It may also be partly due to the novelty of the concept ‘plant-based diet’. Over half of the respondents (54%) had not heard of the term prior to participation in the survey, although there was no significant difference between prior awareness and stages of change.

There were strong differences across stages of change groups with regard to benefit and barrier factors. Those in action/maintenance perceived there to be well-being, weight, health, ethical, convenience and financial benefits of consuming a plant-based diet, whereas those in precontemplation did not recognise these benefits. For those who have not been exposed to the benefits of eating a plant-based diet, an awareness raising strategy could help to increase recognition and credibility. Ethical benefits were strongest among those in contemplation/preparation and action/maintenance. This could be due to people with these kinds of altruistic values being attracted to plant foods because of their ethical connotations. However, it is possible that providing information on the food security, environmental and animal welfare benefits associated with a plant-based diet (Lewis, 1994; Pimentel and Pimentel, 2003) may help to progress people to the action stage. Those in contemplation/preparation are likely to be more susceptible to such information than those who are not considering eating a plant-based diet, as they were found to lack information on plant-based diets. This group would also be likely to benefit from information on availability and preparation of healthier alternatives to foods such as confectionary and fast food, availability of suitable plant-based meals or snacks from food outlets and tips on how to decrease the number of shopping trips (or alternatively how to increase enjoyment of food shopping, such as by attending markets). Such messages could be targeted at younger people, as those in contemplation/preparation were younger than those in the other groups. Those in precontemplation have an even broader range of barriers to overcome before they would be likely to consume a plant-based diet, including health- and family-related barriers and an unwillingness to alter their current diet and reduce their meat consumption. These are the areas that should be focused on by those in the public health nutrition arena and others who wish to progress those in precontemplation with regard to plant-based diets to later stages. For example, education is required about how it is possible to obtain iron and protein from a plant-based diet, and tips on how to make a gradual, easy transition to a plant-based diet. Education and communication should be oriented to the whole family and should distinguish partner opposition as a potential practical constraint. Precontemplators would also need to be provided with ample reasons to make this dietary change – that is, the benefits of change. Greater targeted awareness raising among opinion leaders is one method by which plant foods and plant-based diets could be promoted. Broader change is also required, such as the cooperation of food processors in the production and promotion of healthy and tasty plant-based foods that are attractive to the entire family.

The absence of sex differences between stages of change groups is noteworthy, as previous research has found that women tend to be more health conscious and more likely to be a low meat consumer than are men (Rappoport et al., 1993; Australian Bureau of Statistics, 1997; Fagerli and Wandel, 1999; Kearney et al., 2000; Lea and Worsley, 2004). In addition, a study on stages of change for fruit and vegetables found that those in maintenance were more likely to be women (Van Duyn et al., 1998). Women in the current study did eat significantly less red meat and more fruit and vegetables than did men (data not reported here). However, there were no significant sex differences with regard to other foods such as white meat, legumes, nuts, seeds and whole-meal bread, although women ate eggs significantly more often than did men (data not reported here). Perhaps when the whole diet is considered, rather than food items such as red meat, fruits and vegetables, there is a lack of sex differences with regard to consumption of a plant-based diet. The novelty of the term ‘plant-based diet’ and the possible lack of awareness about the benefits of consumption of a whole range of plant foods may play a role in this finding. Further research is required to corroborate this result.

It is plausible for there to be a difference in vegetarian status between those at the various stages of change to a plant-based diet. Owing to health being a common motivation for choosing a vegetarian or semivegetarian diet (Beardsworth and Keil, 1991; Rozin et al., 1997; Lea and Worsley, 2003a, 2003b) and to the reduced emphasis on meat, there is likely to be an increased emphasis on plant foods. Indeed, previous research has found that vegetarians do consume higher quantities of plant foods than do nonvegetarians (Perry et al., 2002; Haddad and Tanzman, 2003).

Previous research on self-determined stages of change for fruit and vegetable consumption has found that those in the higher stages tend to eat more fruits, vegetables and grains than those in lower stages (Van Duyn et al., 1998, 2001; Greene et al., 2003). In the current study, there were strong differences between stages of change categories and frequency of consumption of a variety of foods of plant and animal origin, despite the subjectivity and complexity of the definition of plant-based diet provided. Those in the highest stages ate more fruit, vegetables, nuts, seeds, whole-meal bread and cooked cereals than those in the other stages, which provide some evidence of validity to the use of self-determined measures of stage of change. However, vegetable and legume consumption was low for all respondents, including those in action or maintenance. The recommended daily intake of vegetables in Australia is five serves or more a day (National Health and Medical Research Council, 2003), so even those in action/maintenance were eating two serves too few. Other surveys have also shown vegetable consumption in Australia to be low (Australian Bureau of Statistics, 1997; Victorian Government Department of Human Services, 2004). One reason for this is that the public is often unaware of the quantity of vegetables that is recommended to be eaten (Lechner et al., 1997; Stables et al., 2002). The legume and vegetable food groups may therefore need to be the key focus of attempts to increase plant food consumption.

A limitation of the study was the modest response rate (51%). However, a response rate of 50% is considered adequate for reporting (Babbie, 1989), and other surveys conducted in Australia and elsewhere have had a lower response rate (Cox et al., 1998; Timperio et al., 2000). It would be useful to conduct a larger study to confirm and expand the present findings, particularly given the small size of some stage of change groups. A larger study could help to decide on the usefulness of the stages of change model for plant-based diets and other complex dietary behaviours, as the finding that the post hoc comparisons do not support the notion of discrete stages may be due to the need to combine some stages. Nonetheless, the study did find differences between stages in plant and animal food consumption, as well as perceived barriers and benefits of plant-based diets and sociodemographic characteristics, which does support the applicability of the stages of change model for plant-based diets. In addition, although we feel that the results of this study may be most appropriately used to devise a variety of public health messages to increase consumption of a broad range of plant foods, rather than messages that explicitly utilise the term ‘plant-based diet’, it would be interesting if future research were to compare the effectiveness of messages that incorporate this term with those that target the separate components of plant-based diets (e.g. ‘eat more vegetables’).

In conclusion, the study found that a large proportion of the population is not yet ready to consume a plant-based diet. The findings on the associations between stages of change, benefits and barriers of plant-based diets and demographic characteristic may be used to help encourage a higher consumption of plant foods and to help progress people from earlier to later stages of change with regard to a plant-based diet. They can be utilised to help provide appropriate nutrition education and advertising, targeted at specific stages of change. In particular, awareness raising of the benefits of plant-based diets and the need for change is necessary for those in precontemplation, while those in contemplation and preparation need practical information, such as on the availability and preparation of healthier foods compared to high-energy, low-nutrient foods. Environmental supports, such as greater availability of plant-based meals in food outlets and government policies that support production, are likely to be useful for those at all stages of change. Future research could examine the willingness of opinion leaders and policy makers to encourage the public to increase their consumption of plant foods and plant-based diets.

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Acknowledgements

The project was supported by the Australian Research Council (DP0209041). EJL is supported by an ARC Postdoctoral Fellowship. DC is supported by a National Health and Medical Research Council/National Heart Foundation Career Development Award.

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  1. Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Deakin University, Burwood, Victoria, Australia

    • E J Lea
    • , D Crawford
    •  & A Worsley

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https://doi.org/10.1038/sj.ejcn.1602320

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