Theory of Planned Behavior Explains Gender Difference in
Fruit and Vegetable Consumption
Amber S. Emanuela
Scout N. McCullya
Kristel M. Gallaghera
John A. Updegraffa
aKent State University
In press, Appetite
Address correspondence to:
John A. Updegraff
Department of Psychology
Kent State University
Kent, OH 44242-0001
A gender difference in fruit and vegetable intake (FVI) is widely documented, but not well
understood. Using data from the National Cancer Institute‘s Food Attitudes and Behavior
Survey, we assessed the extent to which gender differences in FVI are attributable to gender
differences in constructs from the Theory of Planned Behavior (TPB). Females reported more
favorable attitudes and greater perceived behavior control regarding FVI than males, and these
beliefs mediated the observed gender difference. Males reported greater perceived norms for
FVI, but norms did not predict FVI. Gender did not moderate the influence of TPB constructs on
FVI. Thus, TPB constructs substantially explained the gender difference. Interventions targeted
toward adult males may benefit by promoting favorable attitudes and perceived behavioral
control over FVI.
Keywords: Gender; fruit and vegetables; intake; theory of planned behavior.
Using the Theory of Planned Behavior to Explain the Gender Difference in
Fruit and Vegetable Consumption
Nearly all public health authorities recommend fruit and vegetable intake (FVI) as an
important preventive health measure (USDA/USDHHS, 2010; WHO, 2003). People who
consume higher amounts of fruits and vegetables are less likely to be overweight (Lin &
Morrison, 2002) and have a decreased risk of heart disease (Hu, 2003) and certain types of
cancers (Steinmetz & Potter, 1996). FVI is also associated with the prevention of Type 2
diabetes, stroke, chronic obstructive pulmonary disease, cataracts, hypertension, and
diverticulosis (see Van Duyn & Pivonka, 2000 for review). Older adults who consume more
vegetables also experience slower rates of cognitive decline than peers (Kang, Ascherio, &
Grodstein, 2005; Morris, Evans, Tangey, Bienias, & Wilson, 2006).
The U.S. Department of Agriculture and Department of Health and Human Services
(2010) recommend adults consume at least 2 cups of fruits and 2 ½ cups of vegetables per day.
However, adherence to these guidelines is typically low among Americans (Casagrande, Wang,
Anderson, & Gray, 2007; CDC, 2007; Guenther, Dodd, Reedy, & Krebs-Smith, 2006; Serdula et
al., 2004), and demographic differences in FVI are thoroughly established in the literature
(Giskes, Turrell, Patterson, & Newman, 2002; Irala-Estevez et al., 2000; Thompson, Demark-
Wahnefried, et al., 1999).
One robust demographic difference in FVI involves gender (i.e., Friel, Newell, &
Kelleher, 2005; Johansson, Becker, Fagt, Thorgeirsdottir, & Valsta, 1999; Liang, Shediac-
Rizkallah, Celentano, & Rhode, 1999; Roos, Lahelma, Virtanen, Prattala, & Pietinen, 1998;
Thompson, Demark-Wahnefried, et al., 1999; Thompson, Margetts, Speller, & McVey, 1999;
but see Casagrande, Wang, Anderson, & Gary, 2007; Stables et al., 2002 for exceptions).
Women are more likely than men to consume fruits and vegetables (Blanck, Gillespie, Kimmons,
Seymour, & Serdula, 2008) and to meet recommended guidelines (Thompson, Yaroch, et al.,
2011). This gender difference may also be widening. Between 1994 and 2000, both men and
women showed either small declines or no change in their consumption of fruits and fruit juices,
green salad, carrots, and nonfried potatoes. However, women increased their overall
consumption of ‗all other vegetables‘, whereas men did not (Serdula et al., 2004).
Very little evidence exists concerning the psychosocial factors that explain this gap.
Baker and Wardle (2003) examined the extent to which knowledge, attitudes, and preferences
explained gender differences in older British adults‘ FVI. They found that knowledge, but not
attitudes or preferences, partially explained the relationship between gender and FVI. However,
this study did not assess variables from a comprehensive theory of health behavior, limiting the
extent to which it could attribute gender to the psychosocial factors that commonly predict
adherence to preventive health behaviors.
The Theory of Planned Behavior (TPB) is a useful framework for predicting and
explaining people‘s engagement in a variety of health behaviors (Ajzen, 1991; Armitage &
Conner, 2001). The TPB proposes three primary determinants of people‘s intentions and
behaviors: attitudes, perceived behavioral control, and perceived norms. Each of these
determinants is thought to arise from underlying beliefs held by the individual (Fishbein &
Ajzen, 2010). Attitudes reflect the degree to which a person views the behavior as favorable or
unfavorable, and results from beliefs about the outcomes of the behavior and the evaluation of
those outcomes (Fishbein & Ajzen, 2010). For example, favorable attitudes toward FVI could
arise from the belief that FVI provides meaningful health benefits or that fruits and vegetables
taste good. Perceived behavioral control refers to perceptions of the relative ease or difficulty of
performing the behavior; these perceptions are informed by beliefs about the relative power of
internal and external factors to facilitate or impede performance (Ajzen, 1991; Fishbein & Ajzen,
2010). Perceived norms reflect perceptions of social pressure to engage in the behavior, and they
arise from a person‘s beliefs about whether others want him or her to engage in the behavior,
whether others engage in the behavior, and the person‘s motivation to comply.
The TPB has been applied to healthy eating (e.g., high fiber diet, low fat diet, FVI) with
some predictive success (e.g., Conner, Norman, & Bell, 2002; De Bruijn et al., 2007; Kothe, in
press; Paisley & Sparks, 1998; Povey, Conner, Sparks, James, & Shepherd, 2000a; Sjoberg,
Kim, & Reicks, 2004). In a review of 23 studies examining the predictors of FVI, Guillaumie
and colleagues (2010) found the TPB to be a useful model for predicting intentions and behavior
in FVI. These prior studies show that attitudes, perceived norms, and perceived behavioral
control account for anywhere from 30% to 57% of the variance in intentions (Paisley & Sparks,
1998; Povey et al., 2000a), and between 6% and 32% of variance in behavior (Connor et al.,
2002; Povey et al., 2000a). Attitudes and perceived behavioral control typically emerge as the
strongest predictors of healthy eating (Povey, Conner, Sparks, James, & Shepherd, 2000b;
Sjoberg et al., 2004). In contrast, perceived norms often show little or no relationship to healthy
eating (Louis, Chan, & Greenbaum, 2009; Paisley & Sparks, 1998).
Gender and TPB constructs may interact to explain FVI in two ways. First, gender
differences in TPB constructs may explain gender differences in FVI; thus, TPB constructs may
mediate the association between gender and FVI. No studies, to our knowledge, have examined
this question. Second, TPB constructs may differentially predict FVI for males compared to
females; that is, gender may moderate the association between TPB constructs and FVI. In two
prior studies, Blanchard and colleagues (2009a, 2009b) examined this question but did not find
that gender moderated the influence of attitudes, perceived behavioral control, or perceived
norms on FVI.
The aim of the current study was to examine gender differences in FVI through the lens
of the Theory of Planned Behavior. Using data from the National Cancer Institute‘s Food
Attitudes and Behaviors (FAB) survey, we tested two models. One model examined whether
gender differences exist within TPB constructs, and whether these differences explain observed
gender differences in FVI. The second model tested moderation by examining whether TPB
constructs were differentially predictive of FVI for men compared to women.
Study Design and Participants
We analyzed cross-sectional data from the National Cancer Institute‘s Food Attitudes and
Behaviors survey. In the Fall of 2007, the survey was mailed to 5,803 potential adult respondents
in a Consumer Opinion Panel along with a $5 incentive. The final sample consisted of 3,397
participants, corresponding to a response rate of 57%. Sixty percent of the sample was female
and the majority of the sample self-classified as Non-Hispanic Whites (64.38%). Approximately
30% had a high school degree and another 30% had at least some college. Thirty-nine percent of
the sample was between 35 and 54 years of age [Table 1]. The study was approved by the
National Cancer Institute‘s institutional review board.
The FAB survey asked participants a battery of questions concerning their attitudes,
beliefs, and behaviors regarding food, specifically FVI. From these questions, we constructed
three variables that assessed beliefs relevant to the TPB constructs of attitudes, perceived
behavioral control, and perceived norms.
Attitudes. Eleven items in the FAB aligned with the TPB construct of attitudes, assessed
indirectly via behavioral beliefs about FVI. Behavioral beliefs represent the extent to which a
behavior is perceived to produce an outcome, and, in conjunction with evaluation of these
outcomes, determine individuals‘ attitudes toward the behavior (Fishbein & Ajzen, 2010). Six of
these items were prefaced by the stem ―Think about yourself, if you were to eat plenty of fruits
and vegetables every day, how likely would you be to…‖. Participants then responded on a scale
from 1 (―Not at All Likely‖) to 5 (―Very Likely‖) for ―have more energy,‖ ―live a long life,‖
―control your weight,‖ ―look better,‖ ―be ‗regular,‘‖ and ―feel good about yourself.‖ Five other
items were reasons that respondents marked for eating fruits and vegetables: ―it is important for
being as healthy as possible,‖ ―I believe it is a good thing for my health,‖ ―I believe it is very
important for me,‖ ―it is an important choice I really want to make,‖ and ―it is consistent with
my life goals.‖ This 11-item scale had strong reliability, alpha = .90.
Perceived Behavioral Control. Perceived behavioral control represents a personal
evaluation of how easy or difficult the behavior is to perform, and can be assessed using items
relating to a person‘s confidence in his or her ability to perform the behavior (Azjen, 1991;
Fishbein & Ajzen, 2010). One set of questions in the FAB survey asked participants, ―Assuming
that you want to, how confident are you that you could do each of the following starting this
week and continuing for at least 1 month?‖ Respondents answered 7 items related to this stem,
on a scale from 1 (―Not at All Confident‖) to 5 (―Very Confident‖). Items included how
confident they were that they could eat a healthy snack like a fruit or vegetable ―when you‘re
really hungry,‖ ―when you are tired,‖ ―when there are junk foods in your house,‖ ―when your
family and friends are eating junk foods,‖ ―instead of cake, cookies, candy,‖ and ―while
watching TV‖; an additional item asked about confidence to ―buy or bring fruits and vegetables
to eat at work.‖ Reliability for this scale was also strong, alpha = .92.
Perceived Norms. The TPB construct of perceived norms refers to the perceived social
pressure to perform (or not perform) a behavior (Azjen, 1991). As an indirect measure of
perceived norms, we used 8 items from the FAB survey that captured normative beliefs relating
to the perception of social pressure to engage in FVI. Because of limitations in the FAB dataset,
all items represent injunctive norms, or the perception that other people approve of and want the
individual to increase FVI. Three items asked respondents to endorse statements using a 1
(―Strongly Disagree‖) to 5 (―Strongly Agree‖) scale, including ―My friends and family
encourage me to eat fruits and vegetables,‖ ―My family and friends remind me not to eat junk
food,‖ ―My family or friends would say something to me if they saw I was not eating fruits and
vegetables.‖ Five of the questions asked respondents to indicate the extent to which a reason for
FVI was true, on a 1 (―Not True at All‖) to 5 (―Very True)‖ scale. These items included ―others
would be upset with me if I did not,‖ ―I feel pressure from others to eat fruits and vegetables,‖ ―I
want others to approve of me,‖ ―I want others to see I can do it,‖ and ―I don‘t want to let others
down.‖ This 8-item scale had good reliability, alpha = .81.
Fruit and Vegetable Intake (FVI). Detailed questions asked participants about their FVI
over the past month, including juices, fruits, salads, non-fried potatoes, dried beans, other
vegetables, and tomato sauce. An example of phrasing was ―During the last month, how often
did you eat cooked dried beans, such as refried beans, baked beans, bean soup, and pork and
beans?‖ Participants responded on a scale ranging from ―Never‖ to ―Five or more times per day.‖
Following procedures detailed elsewhere (NCI, 2011), responses were converted to cup
equivalent of fruits and vegetables (without fried potatoes) per day.
Gender Differences in Fruit and Vegetable Intake
FVI was positively skewed, ranging from 0 to 50.25 cups per day (M = 3.14, SD = 3.82).
Twenty-eight participants who reported more than 20 cups per day were outliers (+3 SDs from
mean), and were excluded from all analyses. Among the remaining participants, the average fruit
and vegetable intake per day was 2.91 cups (SD = 2.81).
Consistent with prior research, women reported greater FVI than men, t(3198) = -3.38, p
<.001. Women reported FVI of over 3 cups per day (M= 3.04, SD = 2.87), whereas men
reported under 3 cups (M = 2.70, SD = 2.67). This gender difference was also apparent when
examining the proportion of women and men reporting FVI greater than the recommended 4.5
cups per day. A significantly larger proportion of women (20.4%) than men (16.7%) met this
recommendation, χ2(1) = 7.26, p < .01.
Gender Differences in TPB Constructs
Attitude toward FVI was more favorable among females (M = 3.97, SD = .75) than
males, (M = 3.65, SD = .83), t(3301) = -11.31, p < .001. Further, on each behavioral belief item
comprising the attitudes construct, women reported more favorable beliefs than men, p < .001.
Females also reported greater perceived behavioral control over FVI (M = 3.75, SD = .96)
than males (M = 3.50, SD = 1.07), t(3291) = - 6.91, p < .001. Across all items comprising the
construct, women reported higher confidence than males, p < .001.
Males reported greater perceived norms regarding FVI (M = 2.29, SD = .83) than females
(M = 2.13, SD = .81), t(3305) = -5.66, p < .01. On all items except one (―I want others to see I
can do it‖, p > .10), men reported stronger normative beliefs than women.
Do TPB Constructs Mediate Gender Differences in FVI?
To examine whether these gender differences in TPB constructs explain gender
differences in FVI, we used methods described by Preacher and Hayes (2008) which estimate
path coefficients in multiple mediator models and provide bootstrap confidence intervals for
indirect effects. In this meditational model, gender was the independent variable; attitudes,
perceived behavioral control, and perceived norms were mediators; and covariates included age,
education level, ethnicity/race, and geographic location (see Blanck et al., 2011, and Thompson,
Willis et al., 2011, for prior use of these covariates in the FAB survey). We used Hayes and
Preacher‘s (2011) ‗INDIRECT SPSS‘ macro to compute parameter estimates and confidence
Figure 1 displays results from the mediation analysis. Consistent with the TPB, favorable
attitudes predicted greater FVI, β = .14, t(3150) = 7.37, p < .001. More importantly, there was a
significant indirect effect of gender on FVI through attitudes, β = .20, B = .16, CI= .11, .22, p <
.01. [Figure 1]. Ancillary analyses showed that significant indirect effects of three specific
behavioral beliefs drove this effect: ―I personally believe it is a good thing for my health‖ (CI =
05 - .14), ―it is consistent with my life goals‖ (CI = .05, .14), and ―I have carefully thought about
it and believe it is very important for me‖ (CI = .01 - .12).
Greater perceived behavioral control also predicted greater FVI, β = .25, t(3150) = 13.67,
p < .001. There was also a significant indirect effect of gender on FVI through perceived
behavioral control, β = .12, B = .18, CI= .12, .22, p < .01. Ancillary analyses showed that this
effect was driven by significant indirect effects of participants‘ confidence in eating FV in four
specific contexts: ―bringing fruits and vegetables to eat at work‖ (CI=.02 - .10), ―when tired‖
(CI=.02 - .09), ―when there are junk foods in your house‖ (CI=.01 - .08), and ―while watching
TV‖ (CI=.00 - .09).
Perceived norms was not a significant predictor of FVI, β = .03, t(3150) = 1.93, p > .05.
Thus, there was no significant indirect effect of gender on FVI through perceived norms, β = -
.11, B = -.02, CI= -.05, .002, p = .05.
Importantly, gender did not have a significant direct effect on FVI after accounting for
the indirect effects of the TBP constructs, p > .05. Attitudes, perceived behavioral control, and
perceived norms together accounted for 87% of the relationship between gender and FVI. Thus,
gender differences in FVI were adequately explained by the TPB.
Does Gender Moderate Relationships Between TPB Constructs and FVI?
In a second model, we examined whether gender moderated the associations between any
of the TPB constructs and FVI. In this model, we included gender, the three TPB constructs, all
interaction terms between gender and the TPB constructs, and covariates described earlier. All
interactions between gender and TPB constructs were not significant (p‘s > .05), indicating that
gender did not significantly moderate the association between any of the TPB constructs and
The present study aimed to understand the psychosocial factors that may underlie
observed gender differences in fruit and vegetable intake. Consistent with prior research, women
reported more FVI than men. Furthermore, women reported greater perceived behavioral control
and more favorable attitudes toward FVI. In contrast, men reported greater perceived norms
regarding FVI. Most importantly, we found clear evidence that the gender differences in attitudes
and perceived behavioral control significantly mediated the observed gender difference in FVI.
Specifically, American men‘s relatively low FVI was explained by weaker beliefs in the
importance of FVI for health, as well as lesser confidence in the ability to eat FV at work, when
tired, when watching television, and when other junk foods are available.
To our knowledge, the only other study to examine psychosocial factors underlying the
gender difference in FVI (Baker and Wardle, 2003) found that females‘ greater knowledge—but
not attitudes—partially explained the gender difference in FVI. This study, however, focused on
older adults attending a population-based cancer screening in the United Kingdom prior to 2000.
Thus, the discrepancy between our findings and Baker and Wardle‘s (2003) findings may be due
to differences in the age, cultural context, or health motivations of the two samples. For example,
attitudes may better explain disparities in FVI among a population-based sample such as the
FAB respondents, rather than among a sample pre-selected for adherence to recommended health
behaviors, as was Baker and Wardle‘s (2003) sample.
Interestingly, males reported greater perceived norms regarding FVI compared to
females. Our measure of norms assessed injunctive norms, or the perception that other people
approve of and want the individual to increase FVI. Injunctive norms contrast with descriptive
norms, which represent the perception of the extent to which others practice the behavior. The
unexpected finding regarding perceived norms may make sense considering the injunctive nature
of our measure. To the extent that other people perceive men‘s FVI as inadequate, men may
indeed experience greater pressure from others to increase FVI. However, this pressure may not
necessarily influence men‘s intentions and behavior if they misperceive their own FVI as
adequate. Thus, increasing men‘s knowledge of FVI recommendations may be an important step
in addressing gender differences in FVI (cf., Baker & Wardle, 2003).
Perceived norms did not significantly predict FVI in our sample, a finding corroborated
in another review (Shaikh et al., 2008). Perceived norms, particularly descriptive norms, tend to
be weaker predictors of health-promoting behaviors compared to health-risk behaviors, and for
older samples compared to younger samples (Rivis & Sheeran, 2003). Thus, our findings
confirm the limited role of perceived norms in predicting the health-promoting behavior of FVI
Consistent with prior research, gender did not moderate the influence of any TPB
construct on FVI. Thus, there is no reason to expect that a particular TPB construct will be more
motivating for men than for women. Rather, interventions that aim to increase men‘s FVI
consumption should emphasize the TPB constructs on which males tend to report low levels.
The FAB data is cross-sectional, so causality cannot be inferred. Furthermore, as the
study was cross-sectional, it did not include questions about respondents‘ intentions to consume
fruits and vegetables. According to the Theory of Planned Behavior, intention is the most
proximal predictor of behavior, with attitudes, perceived behavioral control and perceived norms
influencing behavior via intentions. Thus, we were unable to test the complete TPB model with
the available data. Despite this theoretical limitation, our results have practical significance, as
interventions more often seek to promote favorable attitudes, perceived behavioral control, and
social norms, rather than directly increase intentions. Thus, of the components of the TPB, this
study included the beliefs and constructs most often targeted in interventions. Lastly, although
the FAB survey utilized a population-based sample, it did not use probability sampling so the
results may not be generalizable to the American population as a whole.
Despite these limitations, our findings demonstrate that among a large sample of
American adults, males reported less favorable attitudes and less perceived behavioral control for
FVI, and these beliefs significantly predicted self-reported FVI. In contrast, perceived norms did
not explain gender differences. Thus, our findings do not support the use of social normative
interventions for promoting FVI among adult American men. Rather, interventions that aim to
increase FVI among adult males may do well to promote favorable attitudes toward fruits and
vegetables and enhance men‘s perceptions of control over increasing FVI.
Preparation of the manuscript was supported by a grant from the National Institute of
Health to the corresponding author. None of the authors have any conflicts of interest.