although cardiovascular disease has been decreased in developed countries , it is increasing in developing countries without noticeable public health responses ( 1 ) . in iran , like other developing countries , cardiovascular disease is the main reason of death and disability ( 2 ) .
it has been indicated that this disease causes about a half of all deaths ( 3 ) .
furthermore , it was revealed that this increased rate has been due to increased major risk factors in iran ( 4 ) .
the major risk factors like hypertension , hypercholesterolemia , smoking and diabetes are increased in this country ( 5 ) .
recognition of patients with vascular disease and intervention with advice about life style , cigarette smoking , alcohol , nutrition and physical activity are among the preventing methods of cardiovascular disease ( 6 ) .
disease preventing methods focus mostly on lifestyle factors such as physical activity , healthy diet and not smoking ( 7 ) .
confederacy of international health education organizations ( cnheo ) declared that theory and technology for the purpose of educational research should be used in methodology designing , performance and evaluation of health education programs .
health belief model is one of the preventive models used for public health problem such as cardiovascular disease .
this model was developed to explain lack of public participation in health screening and prevention programs in the 1950s ( 10 ) .
in addition , this model is used to examine patients ' motivations for adopting a health - related behavior as well as assessing health - behavior interventions .
it includes six key domains of perceived susceptibility , perceived severity , perceived benefits , perceived barriers , cues to action and self - efficacy ( 11 ) .
self - efficacy domain refers to one 's beliefs in one 's capability to organize and execute the courses of action required to achieve given results ( 12 ) . in many evidences ,
self - efficacy has been associated with healthy nutrition ( 13 ) and physical activity behavior ( 14 ) . in previous evidence
, it was focused that higher levels of self - efficacy contributed to physical activity and lower dietary ( 15 ) .
previous studies showed that health belief model is a useful framework for describing the healthy nutrition behavior ( 16 - 19 ) .
moreover , this model has been used in risk reduction of cardiovascular disease in college students ( 20 ) .
considering the importance of behavioral determinants of nutrition and physical activity behaviors due to cardiovascular disease , this study aimed to identify the important predictors of nutrition and physical activity in relation to cardiovascular disease in students of tehran university .
this was a cross - sectional study performed on students of tehran university from october to december 2012 .
a proportional quota sampling was used to select students studying in majors of humanity , basic sciences and technical - engineering in different grades of bs , msc and phd .
inclusion criteria were being student of tehran university and aged between 18 and 55 years .
exclusion criteria were unwillingness to participate in the study and guest student from other universities .
the sample size was calculated as 323 subjects considering  = 5% , statistical power of 90% , p = 0.5 , d = 0.09 and the following equation : considering 10% attrition rate , we added 45 samples , so we totally considered 368 samples . in total , 36% were from engineering field , 11.3% basic sciences field and 52.7% humanity field . a self - administrated questionnaire consisted of four sections
the first section was about demographic characteristics like age , gender , height , weight , level of education and information sources .
the second part consisted of 16 questions regarding knowledge about causes , diagnosis and risk factors of cardiovascular disease , healthy diet and physical activity due to the disease prevention .
the answering options of these questions were as " correct " with score of 1 , " incorrect " and " i do not know " with score of zero .
in this scale , scores below 7 were considered as " weak " , scores 8 - 11 as " average " and scores  12 as " good " .
the third section of the questionnaire consisted of questions regarding health belief model ( hbm ) constructs such as perceived severity ( 4 items ) , perceived benefits ( 5 items ) , perceived barriers ( 11 items ) , self - efficacy ( 4 items ) and cues to action ( 3 questions ) for healthy nutrition and physical activity behaviors due to cardiovascular disease prevention .
these questions were answered through 5-point likert options from totally agree to totally disagree ranged from 1 to 5 . in this
the fourth section of the questionnaire was about nutrition and physical activity behavior ranged from 1 to 4 .
ten specialists , three cardiologists and others in health education field assessed the questionnaire content .
in content validity , changing the format of questions and omitting irrelevant questions were performed .
afterward , mean content validity index ( cvi ) and content validity rate ( cvr ) of the questionnaire calculated as 0.83 and 0.77 , respectively .  
reliability of the scale was calculated through test - retest on 25 homogeneous students with two weeks interval .
the correlation score was 0.73 for knowledge question , 0.71 for perceived susceptibility questions , 0.61 for perceived severity questions , 0.73 for self - efficacy questions , 0.65 for perceived benefits and barriers questions and 0.80 for cues to action questions .
the cronbach s alpha of knowledge questions were 0.66 , 0.62 , 0.51 , 0.54 , 0.68 , 0.50 , 0.70 for perceived severity , perceived susceptibility , perceived benefits , perceived barriers , perceived self  efficacy and perceived cues to action , respectively .
continuous variables were presented as mean  standard division ( sd ) , whereas categorical data were presented as frequency and percentages .
kolmogorov - simirnov test was used to check normal distribution of data . also linear regression with enter method and logistic regression method were used to study association between independent and response variables .
this was a cross - sectional study performed on students of tehran university from october to december 2012 .
a proportional quota sampling was used to select students studying in majors of humanity , basic sciences and technical - engineering in different grades of bs , msc and phd .
inclusion criteria were being student of tehran university and aged between 18 and 55 years .
exclusion criteria were unwillingness to participate in the study and guest student from other universities .
the sample size was calculated as 323 subjects considering  = 5% , statistical power of 90% , p = 0.5 , d = 0.09 and the following equation : considering 10% attrition rate , we added 45 samples , so we totally considered 368 samples . in total , 36% were from engineering field , 11.3% basic sciences field and 52.7% humanity field .
the first section was about demographic characteristics like age , gender , height , weight , level of education and information sources .
the second part consisted of 16 questions regarding knowledge about causes , diagnosis and risk factors of cardiovascular disease , healthy diet and physical activity due to the disease prevention .
the answering options of these questions were as " correct " with score of 1 , " incorrect " and " i do not know " with score of zero . in this scale ,
scores below 7 were considered as " weak " , scores 8 - 11 as " average " and scores  12 as " good " .
the third section of the questionnaire consisted of questions regarding health belief model ( hbm ) constructs such as perceived severity ( 4 items ) , perceived benefits ( 5 items ) , perceived barriers ( 11 items ) , self - efficacy ( 4 items ) and cues to action ( 3 questions ) for healthy nutrition and physical activity behaviors due to cardiovascular disease prevention .
these questions were answered through 5-point likert options from totally agree to totally disagree ranged from 1 to 5 . in this
the fourth section of the questionnaire was about nutrition and physical activity behavior ranged from 1 to 4 .
ten specialists , three cardiologists and others in health education field assessed the questionnaire content . in content validity , changing the format of questions and omitting irrelevant questions were performed .
afterward , mean content validity index ( cvi ) and content validity rate ( cvr ) of the questionnaire calculated as 0.83 and 0.77 , respectively .  
reliability of the scale was calculated through test - retest on 25 homogeneous students with two weeks interval .
the correlation score was 0.73 for knowledge question , 0.71 for perceived susceptibility questions , 0.61 for perceived severity questions , 0.73 for self - efficacy questions , 0.65 for perceived benefits and barriers questions and 0.80 for cues to action questions .
the cronbach s alpha of knowledge questions were 0.66 , 0.62 , 0.51 , 0.54 , 0.68 , 0.50 , 0.70 for perceived severity , perceived susceptibility , perceived benefits , perceived barriers , perceived self  efficacy and perceived cues to action , respectively .
data was analyzed using spss version 18 ( spss inc . , chicago , ill , usa ) .
continuous variables were presented as mean  standard division ( sd ) , whereas categorical data were presented as frequency and percentages .
kolmogorov - simirnov test was used to check normal distribution of data . also linear regression with enter method and logistic regression method were used to study association between independent and response variables .
totally , 368 subjects including 318 female students ( 86.4% ) and 50 male students ( 13.6% ) took part in the study . the mean age of participants was 24.9 years ( sd = 4.55 ) and the mean weight was 59.58 kg ( sd = 11.3 ) .
the mean score of health belief model constructs and cardiovascular disease preventive behaviors are shown in table 2 .   
data are presented as mean  standard deviation . to explore the predictor variables of nutrition and physical activity behaviors , the main independent variables such as knowledge and all health belief model constructs entered the regression model analysis .
accordingly , there was a positive association between knowledge and nutrition behavior ( p = 0.023 ) and a negative association between perceived barriers and this behavior ( p = 0.004 ) .
also in this model , male subjects showed lower mean nutrition behavior compared to female subjects ( p < 0.001 ) .   
abbreviations : b , standardized beta ; s.e . , standard error ; ci , confidence interval .
furthermore , predictor variables of physical activity behavior are shown in table 4 . according to this table , knowledge ( p = 0.011 ) , perceived severity ( p = 0.009 ) and self - efficacy ( p = 0.033 ) showed positive associations with physical activity behavior , but perceived barriers had a negative association with this behavior ( p = 0.019 ) .   
this study investigated how hbm constructs could predict nutrition and physical activity behaviors due to nutrition and physical activity in tehran university students . regarding nutrition behavior
, this study found that gender , knowledge and perceived barrier could contribute to behavior .
accordingly , this study verified that female students had a better nutrition compared to male students .
in consistent with this result , unhealthier nutrition behaviors in male students and lack of physical activity in female students were reported in previous study ( 21 ) .
contrary to this finding , bahreynian and coworkers found that healthy pattern of nutrition behavior in boys was better than girls , so that girls obtained higher body mass index ( bmi ) than boys ( 22 ) .
furthermore , previous evidence verified that determinants of food quality in students of islands university were physical activity behavior , gender , age and the number of meals consumed per day ( 23 ) .
another study demonstrated that there were differences between two genders regarding the receipt dietary fat ( 24 ) . in another study ,
the dietary knowledge and behavior among female students were better than males ( 25 , 26 ) .
thus , it could be argued that in most studies , the important role of gender regarding nutrition behavior has been noticed . however , there are differences between studies to determine the role of gender in nutrition behavior . in the present study ,
therefore , further studies with more male and female students should be performed . in the present study ,
in the study of vassallo , it was revealed that perceived benefits and barriers could improve dietary regime ( 27 ) .
furthermore , oconnell demonstrated that perceived benefit is a strong predictor of dietary behavior among obese teenagers ( 28 ) .
however , in non - obese teenagers , the perceived susceptibility was the important factor predicting nutrition behavior .
it seems that in healthy and unhealthy people , the role of perceived barriers is different so that in healthy people these variables are more effective .
the present study showed that knowledge has less effect on nutrition than the perceived barrier .
however , previous evidence showed a significant relation between knowledge and food intake , so that knowledge has been an effective factor in defining food choice ( 29 )
. moreover , a previous evidence showed that consumers nutrition knowledge was related to label use behavior ( 30 ) .
however , some studies showed no significant associations between knowledge and dietary behavior ( 31 ) .
the present study showed that for physical activity behavior , perceived severity of cardiovascular disease could affect this behavior more than any other factors .
furthermore , in this study it was revealed that perceived barriers could predict physical activity . in consistent with this result ,
a previous study pointed out that physical activity levels of students were influenced by perceived barriers such as fear of strangers , bad weather and many school assignments ( 32 ) .
therefore , motivation for walking should be affected by stressing on perceived benefits of physical activity such as positive health benefits , recreational benefits and a normal weight . in these motivational interviews , personal limitations such as lack of time , getting sunburn because of walking outdoors , non - supportive climate , traffic threat , crimes , etc
garza and coworkers indicated that self - efficacy as a stronger predictor of the health belief model constructs could affect cardiovascular disease prevention behaviors ( 34 ) .
a previous study on patients with multiple sclerosis , self - efficacy and perceived benefits were the main determinants of physical activity ( 35 ) .
furthermore , self - efficacy also predicted oral health behavior in other study ( 36 ) .
parcel and coworkers indicated that self - efficacy plays a significant role in choosing the diets in students ( 37 ) .  
this study indicated that health belief model contrasts could predict the risky behavior of university students regarding cardiovascular disease .
however , more researches are needed to verify other predictors of high risky behaviors in students .
although , this study had some strong points , there were some limitations such as self - reporting of questions responded by the participants .
furthermore , the study was performed through a cross sectional method in which the relations between the variables were not assessed .
although , this study had some strong points , there were some limitations such as self - reporting of questions responded by the participants .
furthermore , the study was performed through a cross sectional method in which the relations between the variables were not assessed .
 background : disease preventing methods focus mostly on lifestyle factors such as physical activity , healthy diet and not smoking . 
 previous studies verified using theory and models to change unhealthy behaviors , so that health belief model ( hbm ) is a useful framework for describing the healthy nutrition behavior.objectives:this study aimed to predict factors related to unhealthy nutrition and inactive life in students of tehran university , tehran , iran based on the health belief model ( hbm).patients and methods : in this cross sectional study , proportional quota sampling from three different educational levels was conducted from october to december 2012 . a self - administered validated instrument based on the health belief model ( hbm ) with 69 items and four sections 
 was used to collect data . in this study through using linear and logistic regression , the effect of body mass index , age , gender , marriage , self - efficacy , cues to action , knowledge , perceived severity , susceptibility , benefits and barriers on nutrition and physical activity behavior were assessed . 
 spss version 18 was used to analyze data.results:totally , 368 students including 318 female students ( 86.4% ) and 50 male students ( 13.6% ) with a mean age of 24.9 years ( sd = 4.55 ) took part in the study . among all independent variables , gender ( p < 0.001 ) , knowledge ( p = 0.023 ) and perceived barriers ( p = 0.004 ) predicted nutrition behavior . in case of physical activity , knowledge ( p = 0.011 ) , perceived severity ( p = 0.009 ) , perceived barriers ( p = 0.019 ) and self - efficacy ( p = 0.033 ) had significance association with physical activity behavior.conclusions:this study indicated that health belief model contrasts could predict the risky behavior of university students due to heart disease . 
 however , more researches are needed to verify the predictors of high risky behaviors in students . 