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Dietary intake and nutrition-related knowledge in a sample of Lebanese adolescents of contrasting socioeconomic status

Maya Nabhani-Zeidan, Farah Naja, and Lara Nasreddine Abstract Background. Socioeconomic status (SES) is postulated to be a major predictor of dietary intake and nutritionrelated knowledge in adults. To date, very few studies have addressed this effect among adolescents. Objective. To explore differences in nutrient intake and nutrition-related knowledge among adolescents of contrasting SES in Lebanon. Methods. In a cross-sectional survey, 209 males and females, aged 17 to 19 years, were recruited from a private university with high tuition and a free public university in Beirut. The participants completed a multicomponent, self-administered questionnaire that inquired about demographic characteristics and nutrition-related knowledge. Three nonconsecutive 24-hour dietary recalls were obtained through interviews. Energyadjusted means of dietary intake and age-adjusted nutrition-related knowledge were compared between groups using a general linear model. Results. Adolescents in the high-SES group consumed more vegetables, meats, and fats and oils (p < .05). Energy and nutrient intake analysis showed that adolescents in the high-SES group consumed significantly higher amounts of calories, protein, fat, vitamin A, vitamin C, and iron (p < .001) and significantly lower amounts of carbohydrates (p < .05). Nutritional knowledge, although high among all participants, was higher in the high-SES group (p < .05). Conclusions. Although both groups showed good nutrition-related knowledge, SES significantly affected dietary intake in a sample of Lebanese adolescents. This warrants consideration of other factors, such as cost and environment, that may modulate eating behavior among adolescents from different socioeconomic strata. The authors are affiliated with the Department of Nutrition and Food Science, Faculty of Agricultural and Food Sciences, American University of Beirut, Beirut, Lebanon. Please direct queries to the corresponding author: Lara Nasreddine, Faculty of Agricultural and Food Sciences, American University of Beirut, P.O. Box 11-0236, Riad El Solh, Beirut 1107-2020, Lebanon; e-mail: [email protected].

Key words: Adolescents, interventions, knowledge, Lebanon, nutrient intake, socioeconomic status, university Introduction Socioeconomic status (SES) has been reported to be a major predictor of mortality and morbidity. Lower SES is, in general, associated with high-risk health behaviors, including poor dietary habits [1–3]. Eating habits developed earlier in life are likely to persist into adulthood; consequently, poor dietary practices in adolescence may constitute an increased risk for several adult chronic diseases [4, 5]. In studies conducted in the United States and various regions in Europe, adolescents often consumed a diet with excess amounts of fat, sugar, and salt and less than recommended amounts of fruits, vegetables, grains, calcium, and iron [6–9]. Adolescents of low SES are often reported to consume a less balanced diet and have been associated with a higher risk of engaging in unhealthy food intake practices as compared with their higher-SES peers [10, 11]. This may indicate that adolescents belonging to lowSES groups may be at a greater risk for nutrition-related disease than those of higher SES. The extent to which nutrition-related knowledge influences dietary practices is controversial, and there is a gap in the literature concerning whether knowledge translates into better eating behavior, particularly among high-risk 17- to 19-year old university students. Some adult studies have found that knowledge about healthy food choices and basic principles of a nutritionally balanced diet does influence dietary behavior and plays a fundamental role in dietary behavior change [12, 13]. Studies in children [14, 15] indicate that although nutrition-related knowledge is necessary for the adoption of a balanced diet, it is not strongly correlated with eating patterns. Several authors from the United Kingdom have proposed that people of lower SES know as much about the

Food and Nutrition Bulletin, vol. 32, no. 2 © 2011, The United Nations University.

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principles of healthy eating as their higher-SES counterparts, but their low earnings render them unable to afford healthy food choices [16, 17]. The effect of SES on dietary intakes of adolescents has been far less explored. Research in the United States and the United Kingdom suggests that adolescents belonging to lowSES groups often engage in unhealthy eating because they may lack appropriate nutrition-related knowledge [18, 19]. On the other hand, Gallagher [20], in a study conducted among UK adolescents, demonstrated that both the low-SES and the high-SES groups had an adequate knowledge and understanding of nutritionrelated principles. We conducted a cross-sectional survey of adolescents belonging to contrasting SES groups in Beirut, Lebanon, a low- to middle-income Eastern Mediterranean country. We specifically chose this population for two reasons. First, although adolescent dietary intakes have not yet been extensively investigated in the region, there is evidence that suggests that this age group may be engaging in unhealthy dietary practices [21]. In addition, examining the relationship of SES to dietary practices and nutrition-related knowledge in this population may provide an overview for possible nutrition intervention strategies specifically tailored to improve dietary intake and practices of Lebanese youth in different SES groups. Also, Lebanon differs considerably from the United States and Europe with regard to food availability and cost. Seasonal fruits and vegetables are widely available throughout the country at affordable prices [22] and are used extensively as part of many traditional ethnic dishes. In this study, we measured differences in adolescent nutrient intake and in nutrition-related knowledge as a determinant of eating behavior between contrasting SES groups within this population. We measured nutritional knowledge as a multidimensional construct, since several researchers contend that three components (dietary guidelines, sources of nutrients, and diet–disease relationships) are needed for the facilitation of healthy eating practices [23, 24].

Methods Research design and study participants

This study is part of a larger study on the development and implementation of a nutrition education intervention among university students from varying socioeconomic strata conducted in fulfillment of a PhD thesis at the University of Leicester, UK. A cross-sectional survey investigating dietary intake and nutritional knowledge was conducted on a convenience sample of 17- to 19-year-old adolescents who were studying for a university degree, living in Beirut, Lebanon, and

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belonging to contrasting SES groups. To allow for the comparison of dietary practices and nutrition-related knowledge of adolescents from high-SES and low-SES communities, sampling was conducted in two different educational institutions. One is among the universities with the highest tuition fees in the country, whereas the second is an institution that provides free education and is mostly attended by individuals of lower SES. In Lebanon, there exist strong social inequalities among those attending universities. At the upper end of the scale, one finds the elite, prestigious universities that enroll the highest proportion of students of high SES, and at the lower end the universities that enroll students of low SES [25–28]. Students registered in different sections of an English course were invited to participate in the study during class by their professors at each university. The professors assured the students that participation was strictly voluntary and explained the aims and procedures of the study. To be eligible for the study, participants had to be first-year university students with normal body mass index (BMI), according to WHO 1995 criteria (BMI < 85th percentile for sex and age), not following a special diet, and free of any chronic disease. Students attending university courses related to medicine or nutrition were excluded to avoid interference owing to specific knowledge about healthy eating [29, 30]. Non-Lebanese students were also excluded from the study. In total, 320 individuals (equally divided among high-SES and low-SES) were invited to participate, but 50 declined due to lack of time. Ten did not meet the inclusion criteria, 28 did not complete the dietary interview, and 23 did not complete the questionnaire. Thus, 110 students from the high-SES group and 99 from the low-SES group were included in the study. Data collection

Data were collected by a multicomponent, self-administered questionnaire that inquires about demographic and anthropometric characteristics and nutritional knowledge, in addition to three nonconsecutive 24-hour dietary recalls. The reproducibility of the questionnaire was verified by a test–retest procedure (3 months apart). Analysis of the scores on the first and second completed questionnaires was done by intraclass correlation (ICC). In general, values over 0.70 are considered as high agreement; the ICC for the questionnaire was 0.79 (95% confidence interval, 0.66 to 0.89). Written informed consent was obtained from all participants at the beginning of the study. Ethical approval was obtained from the University of Leicester School of Education. The participants were informed that they could drop out of the study at any time.

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Dietary intake and nutrition-related knowledge

Demographic and anthropometric characteristics

Data on demographic characteristics (age, sex, height, weight, and school attended before university) were obtained from all participants. Nutritional-knowledge questionnaire

Based on the premise that nutritional knowledge is multidimensional and thus should be measured as such [31, 32], and in accordance with McPherson and Turnbull [24] and De Vriendt et al. [23], the nutritional-knowledge questionnaire used in this study covered three proposed constructs of nutritional knowledge [32]. This questionnaire consists of 38 questions, divided into three subscales of nutritional knowledge measuring knowledge of what constitutes healthy eating, knowledge of how to make good dietary choices, and knowledge of diet–disease relationships. Knowledge of what constitutes healthy eating was measured by part 1, the “dietary guidelines” subscale; knowledge of how to make good dietary choices was measured by part 2, the “sources of nutrients” subscale; and knowledge of diet–disease relationships was measured by part 3, the “diet–disease” subscale. The maximum scores for parts 1, 2, and 3 were 5, 1, and 1, respectively. The maximum total nutritional knowledge (TNK) score was 7. Assessment of dietary intake

Dietary intake for each participant was assessed by three nonconsecutive 24-hour dietary recalls conducted by a nutritionist on two weekdays and one weekend day. A standardized interview protocol was used following the US Department of Agriculture guidelines [33, 34]. Common household measures (measuring cups, spoons, and a ruler) were shown to assist in estimation of portion size. Foods were grouped into milk, grains, fruits, vegetables, meats, and fats and oils. Assessment of dietary intake was performed by comparison of food group analysis with My Pyramid recommendations for an average 2,000-kcal diet [35] and comparison of micronutrient intake and percentage of

contribution to energy by macronutrients with Dietary Reference Intakes (DRIs) [36]. Statistical analysis

The distributions of demographic factors and of mean weight, height, and BMI were compared between lowSES and high-SES groups by the chi-square test for categorical variables and the independent t-test for continuous variables. Differences in mean consumption of the various food groups were assessed by the independent t-test. Food consumption data provided by the 24-hour dietary recalls were converted to energy and nutrient intakes by using Nutritionist IV software (N-Squared Computing), and the Middle East Food Composition Tables were used to analyze data on local dishes [37]. Energy and energy-adjusted means of dietary intake were compared between SES groups by a general linear model using energy as covariate, dietary intake as dependent variable, and SES as the fixed factor. Similarly, a general linear model using age as covariate, nutritional knowledge as dependent variable, and SES as the fixed factor was performed to investigate possible age-adjusted differences in both TNK and independent constructs of nutritional knowledge between the low-SES and high-SES groups. Differences were considered significant at p < .05. Statistical analysis was performed with SPSS, version 13.0.

Results Study sample characteristics

One hundred ten high-SES and 99 low-SES adolescents participated in the study (table 1). The distribution of study participants across the low-SES and high-SES groups was further confirmed by the type of school attended before university: all high-SES adolescents had attended private schools and all low-SES adolescents had attended public schools. Dietary intake

The intakes of various food groups, as determined

TABLE 1. Comparison of sample characteristics between high-SES and low-SES groups Characteristic Age (yr)—mean ± SD Male sex—% Height (cm)—mean ± SD Weight (cm)—mean ± SD BMI (kg/m2)—mean ± SD

High-SES (n = 110)

Low-SES (n = 99)

p

18.28 ± 0.96 39.1 170.15 ± 8.16 65.67 ± 14.11 22.51 ± 3.76

17.59 ± 1.05 49.5 163.30 ± 10.08 58.15 ± 11.66 21.73 ± 3.50

< .001 .130 < .001 < .001 .142

BMI, body mass index; SES, socioeconomic status

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M. Nabhani-Zeidan et al. 14

HSES

LSES

MyPyramid *

Mean consumption (servings/day)

12 *

10

8

*

6

4 *

2

*

*

*

*

*

0

Milk

Grains

Fruit

Vegetables

Meats Fats and oils

FIG. 1. Mean consumption of food groups by high-socioeconomic status (HSES) and low-socioeconomic status (LSES) groups as compared with MyPyramid recommendations. Recommendations are based on a 2,000-kcal diet. *Significant (p < .05) difference between HSES and LSES groups

from the three nonconsecutive 24-hour dietary recalls, are presented in figure 1. The high-SES group had a significantly higher consumption (servings/day) of vegetables (1.93 ± 0.11 for high-SES, 1.44 ± 0.20 for low-SES), fats and oils (12.91 ± 0.30 for high-SES, 10.60 ± 0.53 for low-SES), and meats (1.56 ± 0.06 for high-SES, 0.80 ± 0.11 for low-SES). Energy intake in the high-SES group (1,815.89 ± 899.26 kcal/day) was significantly higher than that in the low-SES group (1,452.03 ± 784.04 kcal/day). Similarly, the contributions of fat and protein to daily energy intake were significantly higher among high-SES adolescents (39.62% and 13.91%, respectively) than among their low-SES counterparts (30.32% and 10.98%, respectively). Carbohydrate intake in the low-SES group was significantly higher (58.61%) than that in the high-SES group (47.81%).

The daily means of energy and energy-adjusted nutrient intakes are presented in table 2. In addition to macronutrients, dietary intake analyses were also conducted for fiber and two vitamins (vitamin A and vitamin C) and two minerals (calcium and iron), the micronutrients that are required to be listed on food labels. The high-SES group had a substantially higher intake (g/day) of protein (58.52 ± 1.30 for high-SES, 49.53 ± 2.31 for low-SES) and fat (77.23 ± 1.51 for high-SES, 63.37 ± 2.69 for low-SES) and a lower intake of carbohydrate (g/day) (204.74 ± 3.64 for high-SES, 245.28 ± 6.51 for low-SES) (p < .05), while no differences were observed for fiber. Similarly, the intakes (mg/day) of vitamin A (728.50 ± 54.25 for high-SES, 364.56 ± 96.92 for low-SES), vitamin C (117.38 ± 7.59 for high-SES, 80.43 ± 13.55 for low-SES), and iron (10.87 ± 0.32 for high-SES, 8.36 ± 0.57 for low-SES)

TABLE 2. Comparison of selected energy-adjusted mean (± SE) nutrient intakes between high-SES and low-SES groups Nutrient Energy (kcal) Carbohydrates (g) Protein (g) Fat (g) Fiber (g) Vitamin A (RE) Vitamin C (mg) Calcium (mg) Iron (mg)

High-SES (n = 116) 1,815 ± 899.26 204.74 ± 3.64 58.52 ± 1.30 77.23 ± 1.51 12.66 ± 0.40 728.50 ± 54.25 117.38 ± 7.59 519.36 ± 17.72 10.87 ± 0.32

% DRI 157.5 119.4 45.2 91.1 167.0 40.0 83.6

Low-SES (n = 99) 1,452 ± 784.04 245.28 ± 6.51 49.53 ± 2.31 63.37 ± 2.69 13.25 ± 0.71 364.56 ± 96.92 80.43 ± 13.55 531.17 ± 31.65 8.36 ± 0.57

DRI, Dietary Reference Intake; RE, retinol equivalent; SES, socioeconomic status

% DRI

p

188.7 101.1

< .001 .001 < .001 .462 .001 .019 .746 < .001

47.3 45.5 114.9 40.9 64.3

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were higher in the high-SES than in the low-SES group (p < .05). No differences were observed for calcium. Nutrition-related knowledge

Since the subjects’ age was significantly correlated with the score on part 1 of the nutritional-knowledge questionnaire (r = 0.195; p = .008), age was taken into account as a covariate. The results of the linear regression adjusted for age (table 3) indicate that there was a significant difference in nutritional knowledge (p < 0.05) for part 3 and TNK among the different SES groups. In order to investigate possible associations between SES and nutritional knowledge, only TNK was considered.

Discussion The present study is the first to examine food and nutrient intakes and nutrition-related knowledge among adolescents of different SES groups in Lebanon and the Eastern Mediterranean Region. Although we found significant differences between the groups in dietary intake and total nutritional knowledge (TNK), the latter was high among both groups. The intake of macronutrients differed significantly between the low-SES and high-SES groups, with the low-SES participants consuming lower amounts of protein and fat but higher amounts of carbohydrates than their highSES counterparts. With the exception of calcium, the low-SES group had lower intakes of the studied micronutrients. The gaps between reported micronutrient intakes and the DRIs were larger for the low-SES than for the high-SES group. The lower intake of protein in the low-SES group is in agreement with previous research from the United Kingdom [10], where young people belonging to households of lower-income groups had a lower mean intake of protein. On the other hand, the lower TABLE 3. Comparison of age-adjusted mean (± SE) nutritional knowledge scores between high-SES and low-SES groups Component of score

High-SES

Low-SES

p

Nutritional knowledge 1—dietary guidelines Nutritional knowledge 2—nutrient sources Nutritional knowledge 3— diet–disease relationships TNK

3.29 ± 0.04

3.35 ± 0.04

.323

0.75 ± 0.01

0.72 ± 0.01

.056

0.56 ± 0.02

0.13 ± 0.02

< .001

4.59 ± 0.06

4.20 ± 0.06

< .001

SES, socioeconomic status; TNK, total nutritional knowledge

intake of fat in the low-SES group in our study is inconsistent with findings from studies in the United Kingdom that have reported either similar fat intakes in low- and high-SES groups of adolescents [10] or higher fat intakes in low-SES than in high-SES groups [20]. The association between higher fat intake and high SES observed among adolescents in our study is in agreement with findings reported from other developing countries, where children and adolescents from higher-income families are more likely to adopt unhealthy dietary practices, such as consumption of high-fat fast foods and energy-dense snacks [38, 39]. Similarly, the higher intake of carbohydrate observed among the low-SES group in our study is inconsistent with findings from the United States [40] and Europe [10], where carbohydrate consumption was found to increase with increasing SES. This difference between our results and the US and European results may be due to the fact that bread is one of the major staple foods in Lebanon and is available at low cost, since its production is subsidized by the government. In this study, the low-SES adolescents had significantly lower intakes of vitamin A, vitamin C, and iron. These findings are consistent with studies targeting adolescents in the United States, the United Kingdom, and Europe that have found lower mean daily intakes of these nutrients among children and adolescents belonging to low-SES households than among their high-SES counterparts [7, 8, 10, 41]. The lower iron intake in the low-SES group may be due to their lower consumption of meat, which is one of the primary sources of iron. The low-SES group also had lower intakes of vegetables and milk, which may explain their lower vitamin A intake. The estimated intake of calcium by adolescents in both the high-SES and the low-SES samples was less than half the recommended value for this age group [35]. This is in agreement with recent research that has found a decrease in the intake of calcium by adolescents in recent years [7, 8, 20, 42]. Researchers attribute this decrease to a decrease in the consumption of milk and milk products and an increase in the consumption of soft drinks and other beverages by adolescents [8, 10, 42]. Similarly, the findings of this study indicate that both the low-SES and the high-SES adolescents consumed less than the recommended amount of dairy products [35]. Vitamin C intake was adequate in both groups, as compared with the recommended value, although it was lower in the low-SES group. The adequate vitamin C intake may be attributed to the high consumption of fruits by both groups [35]. Studies from the United States and Europe [6, 7, 9, 20, 42, 43] found that adolescents consumed lower than recommended intakes of fruits and vegetables. Similar results have been reported in the Eastern Mediterranean Region among children and adolescents residing in the Syrian capital, Damascus, and its suburbs [44].

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Our results do not fully agree with the cited studies with regard to fruits; adolescents in both SES groups had adequate intakes of fruits, and the difference between the groups in fruit intake was small and did not reach statistical difference [35]. This is consistent, in part, with recent findings for Lebanese adults [22] and for adolescents in southern Europe and European Mediterranean countries, such as Greece, where the subjects had adequate intakes of fruits and vegetables as part of the Mediterranean-type diet [41, 45]. Fruit consumption in the current study must be viewed in the context of the high availability and accessibility of fresh produce in Lebanese markets throughout the year. Fruits are a significant component of the traditional Lebanese diet, and their abundance at relatively affordable prices makes the situation different from that in the United States and Europe when cost considerations are taken into account. Even though TNK was lower among the low-SES adolescents, both SES groups had a high level of nutritional knowledge. This is in agreement with the results of Temple et al. [46], who reported high nutritional knowledge scores among South African adolescents. However, US studies [47, 48] have often presented a different picture, with adolescents having, in general, a low level of nutritional knowledge. When the subscale scores in our study were examined independently of each other, the scores were highest for nutritional knowledge 1 (dietary guidelines) and 2 (sources of nutrients), demonstrating that both the low-SES and the high-SES groups were well aware of dietary guidelines and how to put them into practice. Nutritional knowledge 3 (diet–disease relationships), which has been proposed as a crucial part of the link between awareness and dietary choice [23, 24], was the lowest in both SES groups. Nutritional knowledge 3 was considerably lower in the low-SES than in the high-SES group, but the groups had similar scores for nutritional knowledge 1 and 2. These results are not fully consistent with other research. Our results for nutritional knowledge 1 and 2 are similar to those of Gallagher [20], who found comparable knowledge of healthy eating principles among UK adolescents from different SES groups, but differ from those of Hart et al. [19], who found that knowledge of food-group schemes and classification of foods into “good” and “bad” categories among 7- to 11-year olds was higher for those belonging to high-SES groups. Studies of knowledge of diet–disease relationships, per se, among members of different SES groups are scarce. The only study that we were able to locate examined UK children’s knowledge of links between diet and dental caries and obesity and found no differences among SES groups [19]. However, comparisons of associations with SES in other studies should be done with caution, since studies use different methods for measuring SES, and few, if any, studies conceptualize and measure nutritional knowledge as a

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multidimensional construct [23, 24]. Several European studies found that adults of low-SES groups consume less healthy diets [24, 49]. However, studies on European children reported no association between SES and healthy food habits [50, 51], and the results of studies on European adolescents are inconsistent [11, 20, 46, 52]. With the exception of fruits and vitamin C, our results suggest that the diets of both high- and low-SES adolescents are inadequate when compared with recommendations. The finding that high TNK was not translated into healthy dietary practices among both groups in our study is consistent with previous findings [19, 20, 46] and suggests that traditional nutrition education models that emphasize increasing the knowledge of participants may not be the best approach for eliciting behavior change. Furthermore, some studies have argued that raising the awareness of diet–disease relationships among individuals is crucial for changing poor dietary habits [23, 24]; however, in the present study this did not hold true, particularly for the highSES adolescents, who scored high on the diet–disease relationships component. These results suggest that behavioral focus may be a necessary component for effective intervention. The findings of this study may be limited by the fact that the samples were nonrandom convenience samples. Consequently, the chosen samples are not representative of the population of 17- to 19-year-old adolescents in Lebanon and the findings cannot be readily generalized, although they may be transferable to similar situations and replication may build further confidence in the conclusions of the study. Another limitation of this study is the small sample size, which could have led to a type II error (failing to find a significant difference where a difference existed). Therefore, larger studies are warranted to reveal further differences in intakes and nutritional knowledge between high-SES and low-SES groups. It is also necessary to consider the limitations of self-reported data, as well as factors believed to influence dietary intake, such as sex, physical activity, smoking habits, and consumption of foods away from home, which were not accounted for in the study. That being said, differences in relation to some of these factors appear to be less pronounced in adolescence than in other periods of life. For example, physical activity and dietary behaviors among adolescents are thought to be related [53, 54]; however, mixed results are found in the literature, particularly for different age groups [55, 56] and when covariation of physical activity and diet is studied over time [53, 55]. As for the influence of sex on dietary intake among adolescents, it is likely that girls are more weight- and/ or image-conscious than boys and are more likely to consume fruits and vegetables and practice weightcontrol behaviors [57, 58]. Nevertheless, among similar age groups, conflicting results do exist, where some

Dietary intake and nutrition-related knowledge

studies have reported no effect of sex on dietary intake, fat intake, dietary patterns, or diet quality [59–62]. Eating away from home, which increases in frequency as adolescents move away from home and acquire more autonomy, has been associated with poor eating habits, such as high total energy, total fat, saturated fat, cholesterol, and sodium and low nutrient densities for dietary fiber, calcium, vitamin C, and folate [57]. Additionally, smoking has been associated with a lower food intake, which may be attributed to an induced decrease in appetite [63] or an under-reporting of dietary intake; however, the latter has been studied mainly in adults [64]. The university and college arenas represent the final opportunity for nutrition education of a large number

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of students from the educator’s perspective. The current findings support the need for behavior-based, rather than knowledge-based, interventions designed to improve the dietary intake and practices of Lebanese adolescents and to concurrently encourage such groups to maintain healthful dietary behaviors consistent with the traditional Lebanese diet. Furthermore, this study suggests that the traditional “one size fits all” approach often used in interventions may not be effective among different SES groups. Future research should be directed toward interventions that are culturally appropriate and SES-specific, since different mediators of eating practices, particularly cost, seem to play a major role among low-SES groups in less industrialized societies.

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