Over the last few decades, more and more developing countries have been undergoing a marked shift in the overall structure of their dietary pattern, with an increase in nutrition-related non-communicable diseases (CVD, diabetes and obesity)(Reference Kim and Popkin1). This major dietary change, known as ‘Westernisation’ of the diet, includes a considerable increase in the consumption of fat, particularly saturated fat, and added sugar and sweets in the diet(Reference Popkin2). It also leads to a marked increase in the consumption of animal food products contrasted with a reduction in the consumption of fruit, vegetables and total cereals, and in fibre intake.
Over the same period, migration from developing countries to more industrialised ones has been continuous. In this context, migrant studies contribute important knowledge relating to the ways in which changes in environmental, dietary and lifestyle behaviours affect health and disease status. Indeed, migration and acculturation are associated with significant changes in dietary patterns(Reference Neuhouser, Thompson, Coronado and Solomon3). Several studies have shown that migrants adopt the dietary patterns of their new host country, resulting in negative consequences for health(Reference Cardoso, Hamada, de Souza, Tsugane and Tokudome4–Reference Anderson, Bush, Lean, Bradby, Williams and Lea6). However, the extent of these changes varies with each ethnic group(Reference Misra and Ganda7).
Acculturation is defined as ‘the process by which immigrants adopt the attitudes, values, customs, beliefs, and behaviours of a new culture’(Reference Abraido-Lanza, Armbrister, Florez and Aguirre8). Health-related behaviours, such as dietary patterns and physical activity, of migrants are likely to be affected by the process of acculturation(Reference Perez-Escamilla and Putnik9). For example, the length of residence in the new environment, which is one of the indicators of acculturation, is likely to lead to changes in diet and in physical activity(Reference Perez-Escamilla and Putnik9–Reference Yang, Chung, Kim, Bianchi and Song12). On the other hand, past and current exposure to the socio-cultural norms of the home country could underplay the influence of the new environment. Lifestyles that are related to these norms, such as dietary patterns, alcohol consumption or tobacco use, may be retained to a greater or lesser extent in the new place of residence(Reference Parkin and Khlat13).
In France, adult migrants from southern Europe and North Africa reported dietary practices consistent with the typical Mediterranean diet, which is well known for its positive effects on health(Reference Wanner, Khlat and Bouchardy14, Reference Darmon and Khlat15). Also, a previous study of Tunisian migrant men in France showed that these migrants exhibited better diet quality than their French counterparts, while their diet profile was very similar to that of non-migrant Tunisians(Reference Mejean, Traissac, Eymard-Duvernay, El Ati, Delpeuch and Maire16). Moreover, an active lifestyle was more prevalent among Tunisian migrant men than among local-born French and non-migrant Tunisians(Reference Mejean, Traissac, Eymard-Duvernay, El Ati, Delpeuch and Maire17). Thus, in spite of a rapid nutrition transition in their home country(Reference Mokhtar, Elati, Chabir, Bour, Elkari, Schlossman, Caballero and Aguenaou18, Reference Bouguerra, Alberti, Salem, Rayana, Atti, Gaigi, Slama, Zouari and Alberti19), Tunisian migrants appear to have conserved some healthy behaviours. However, the question arises as to what the respective degree of influence of acculturation and of strength of ties with the country of origin has been in relation to these features over the last 20 years. This last dimension is particularly interesting in the context of North African migration in France. As the two countries are geographically close and have a common historical context, the maintenance of ties with the home country among Tunisian migrants is relatively common and could potentially influence lifestyles related to health. The aim of the current study was to explore the potential associations of dietary patterns and physical activity levels among Tunisian migrant men with their degree of acculturation in France and with their past and current exposure to socio-cultural norms of their home country.
Methods
Design and sampling
The current study presents an analysis of data from a retrospective cohort study which compared Tunisian migrant men aged ≥18 years and two non-migrant male groups: local-born French individuals and non-migrant Tunisians(Reference Mejean, Traissac, Eymard-Duvernay, El Ati, Delpeuch and Maire16, Reference Mejean, Traissac, Eymard-Duvernay, El Ati, Delpeuch and Maire17). In the present study, the subjects were those from the migrant group: migrants were defined as individuals who were native of Tunisia and who had been residing in the South of France (Languedoc-Roussillon region) for more than 1 year at the time of the survey. As French law does not allow access to nominative files with ethnic status, random sampling was not possible. Thus, using the French National Institute of Statistics (INSEE) database, we performed quota sampling based on age and place of residence. The number of migrants surveyed (n 150) was based on power calculations for comparison of the three groups in the first study.
The research complied with the principles of the Helsinki Declaration. The protocol was approved by the French National Commission of Information Technology and Freedom (CNIL). All interviewees gave their free written informed consent.
Data collection
Data were collected in 2004 in France by interviewers who were bilingual in French and Arabic. We specifically trained and standardised interviewers for physical activity and food consumption measurements.
Assessment of economic factors
To assess economic status, correspondence analysis was performed on the matrix of indicator variables coding characteristics of dwelling, utilities and appliances. The score of each household on the first principal component was used as a summary index of household wealth(Reference Traissac, Delpeuch, Maire and Martin-Prével20, Reference Martin-Prevel, Traissac, Delpeuch and Maire21) and the latter was introduced in analyses after breakdown into tertiles of increasing economic level (low, medium and high).
Assessment of acculturation and exposure to socio-cultural norms of the home country
The potential degree of acculturation was assessed by an exposure indicator: length of residence in France, which was derived from the year of arrival. We categorised length of residence in such a manner that there was a substantive variation in length of residence between groups (≤9 years, 10–29 years and ≥30 years) and a minimum sample size in each group.
To evaluate the different periods of past exposure to socio-cultural norms of the home country, age at migration was used. Age at migration was also classified into three groups: ≤20 years old, 21–29 years old and ≥30 years old.
Current exposure to socio-cultural norms of the home country was assessed by an index of social ties with the home country, based on five variables: (i) remittance behaviour for family in the country of origin; (ii) language preference; (iii) home ownership in Tunisia; (iv) having returned to the home country for a holiday during the past year; and (v) projecting to return to the home country after retirement. This summary index was built in a similar way to the economic index by correspondence analysis. It was also categorised into three levels (tertiles): distant, moderate and close ties with the home country.
Assessment of dietary intake
To assess usual dietary intake during the past month, a validated quantitative FFQ(Reference Daures, Gerber, Scali, Astre, Bonifacj and Kaaks22) was adapted to Tunisian habits. After creation of a food composition table from a database compiled from the US Department of Agriculture’s food composition database(23) and the French food composition table(Reference Favier, Ireland-Ripert, Toque and Feinberg24), which was relevant for both France and Tunisia, dietary intake data were converted into nutrient data using the ESHA Food Processor software version 8·3 (ESHA Research Inc., Salem, OR, USA).
As there is no internationally acknowledged recommendation for the classification of food groups, we defined eleven food groups: cereals; vegetables; fruits; nuts/beans; fats; sugar/sweets; milk products; meat; fish; eggs; and others (coffee, tea and condiments). The percentage contributions of these eleven food groups to total energy intake were calculated from the mean daily intake (g) of each food group.
Assessment of physical activity level
To evaluate the physical activity level (PAL), we used a frequency questionnaire that assessed the time spent on different current activities: occupational habits, home activities, recreational activities, sports and travel to and from places during the last month, with specific attention to working days and holidays. Total daily physical activity (PA) (MET-h/d) was estimated by adding the product of the time reported for each item by a MET value specific to each category of PA using a published compendium of physical activities(Reference Ainsworth, Haskell and Whitt25) and expressed as a daily average MET score (where MET is metabolic energy equivalent task; 1 MET = 1 kcal/kg per h). We estimated the BMR from the weight, height and age of each person using the Henry equation(Reference Henry26). We then calculated the total energy expenditure (TEE; kcal/d) from BMR and total daily PA. The PAL, expressed as a BMR multiple, was assessed by PAL = TEE/BMR.
Statistical analyses
Effects of length of residence, age at migration and social ties with the home country on physical activity level, percentage of time spent in leisure-time activities, percentage of time spent in occupational activities and dietary characteristics were assessed using general linear models. Dietary characteristics included percentage contributions of food groups and macronutrients to total energy intake, quantities of selected components, ratio of PUFA to SFA and ratio of MUFA to SFA. In the first set of models, effects were adjusted for age and economic level and the models relating to dietary data were also adjusted for energy intake. Then, the effect of length of residence, age at migration and social ties with the home country were also adjusted for each other to control for potential confounding. These potential confounding factors were added sequentially in the models. For example, the effect of length of residence was first adjusted for age at migration, then for social ties with the home country. In order to reduce residual confounding, length of residence and age at migration were used as continuous confounding variables(Reference Becher27).
The type I error rate was set at 0·05. Data entry and quality checks were performed using the Epidata software version 3·1 (Epidata Association, Odense, Denmark); data management and statistical analyses were performed using the Statistical Analysis Systems statistical software package version 9·1 (SAS Institute, Cary, NC, USA).
Results
As three surveyed migrants subsequently withdrew their consent, the final total of subjects used in the analyses was 147.
General characteristics of Tunisian migrants
The mean age of migrants was 50·2 (sd 13·2) years, their mean length of residence and age at migration were respectively 23·0 (sd 12·0) years and 28·2 (sd 10·2) years (Table 1).
General characteristics of Tunisian migrants, South of France, 2004
More than two-thirds (70·7 %) of migrants reported they were currently working, 72·8 % were married and 38·1 % had a low education level. By construction, subjects were evenly split between the three categories of the economic index. Prevalence of smoking was 28·6 % and only 19·1 % of migrants were alcohol consumers (Table 1). The mean BMI of the sample was 26·2 (sd 5·1) kg/m2. Over 40 % of the subjects were above the cut-off values for BMI and waist circumference.
Effects of length of residence
Compared with men who had lived in France for less than 10 years, migrants who had been in France for longer presented a higher percentage contribution of meat to energy intake (P = 0·04) and higher Na intake (P = 0·04), both before and after adjustment for age at migration and ties with the home country (Table 2). They also consumed a lower percentage contribution of sugar and sweets (P = 0·04) and a lower percentage of carbohydrates (P = 0·03) than short-term migrants.
Physical activity and dietary characteristics according to length of residence: Tunisian migrants, South of France, 2004
*Model 1 adjusted for age, economic level, energy intake (only food groups and nutrient characteristics).
†Model 2 adjusted for age, economic level, energy intake (only food groups and nutrient characteristics) and age at migration.
‡Model 3 adjusted for age, economic level, energy intake (only food groups and nutrient characteristics), age at migration and social ties with the home country.
There was an effect of length of residence on physical activity level (P = 0·04), mean percentage contribution of fats (P = 0·02), mean percentage contribution of lipids (P = 0·03), fibre intake (P = 0·03) and MUFA:SFA ratio (P = 0·0005) but the effect disappeared after adjustment for age at migration (Table 2). The difference in the mean percentage contribution of protein was no longer significant after adjustment for social ties with the home country (P = 0·07).
Effects of age at migration
Men who migrated to France before 21 years of age had a significantly higher Na intake than migrants who were older than 21 when they arrived, whether before (P = 0·01) or after adjustment for length of residence and ties with the home country (P = 0·02) (Table 3).
Physical activity and dietary characteristics according to age at migration: Tunisian migrants, South of France, 2004
*Model 1 adjusted for age, economic level, energy intake (only food groups and nutrient characteristics).
†Model 2 adjusted for age, economic level, energy intake (only food groups and nutrient characteristics) and age at migration.
‡Model 3 adjusted for age, economic level, energy intake (only food groups and nutrient characteristics), age at migration and social ties with the home country.
On the other hand, the effect of age at migration on the mean percentage contribution of cereals (P = 0·03), fats (P = 0·04), sweets (P = 0·01), meat (P = 0·003), cholesterol intake (P = 0·004) and on MUFA:SFA ratio (P = 0·0001) was no longer significant after adjustment for length of residence (Table 3).
Effects of social ties with the home country
The mean physical activity level (1·75 (sd 0·18)) was within the ‘active lifestyle’ range. Compared with men who had closer social ties with their home country, men who maintained distant ties had a lower physical activity level and a lower percentage of time spent in occupational activities after adjustment for length of residence (P = 0·01 and P = 0·008, respectively) (Table 4). Concerning food groups, men who had close social ties with their home country had a higher percentage of energy from fats and a higher MUFA:SFA ratio both before (P = 0·0006 and P = 0·0006, respectively) and after adjustment for age at migration (P = 0·009 and P = 0·02, respectively) and length of residence (P = 0·01 and P = 0·02, respectively) than men who had moderate or distant ties with Tunisia (Table 4).
Physical activity and dietary characteristics according to social ties with the home country: Tunisian migrants, South of France, 2004
*Model 1 adjusted for age, economic level, energy intake (only food groups and nutrient characteristics).
†Model 2 adjusted for age, economic level, energy intake (only food groups and nutrient characteristics) and age at migration.
‡Model 3 adjusted for age, economic level, energy intake (only food groups and nutrient characteristics), age at migration and social ties with the home country.
By contrast, the difference in the percentage contribution of cereals (P = 0·04) was no longer significant after adjustment for age at migration (P = 0·18). The effect of social ties on percentage of dairy products (P = 0·02) did not remain significant after adjustment for length of residence (P = 0·13) (Table 4).
Discussion
The originality of our study lies in the use of age at migration and of social ties to evaluate past and current exposure to the home country. Age of migration has been widely taken into account in research on cancer epidemiology, in order to disentangle exposure in early life from the influence of the new environment(Reference Parkin and Khlat13, Reference Andreeva, Unger and Pentz28). This variable has also been used in studies relating to other diseases(Reference Jaber, Brown, Hammad, Zhu and Herman29) or lifestyles(Reference Evenson, Sarmiento and Ayala30–Reference Hosper, Nierkens, Nicolaou and Stronks33). To our knowledge, no study has measured current exposure to socio-cultural norms of the country of origin. Owing to geographical proximity and historical and economic links between France and Tunisia, the context of North African migration in France facilitated the measurement of this dimension.
Influence of acculturation
With increasing length of residence, migrants had a higher consumption of carbohydrates and a lower Na intake. Detailed analysis showed that the increase in carbohydrates was due to increasing consumption of sugar and sweets with length of residence, whereas the contribution of sources of complex carbohydrates (cereals and beans) remained stable. The lower Na intake among long-term migrants was linked to their lower consumption of meat. A French national survey revealed a change in eating patterns with increasing consumption of sweets and sodas and decreasing consumption of meat(Reference Volatier34). Thus, it seems there was a convergence of the consumption of these food groups to that of the host population along with acculturation. These results are in concordance with other studies that showed a diet higher in simple sugars and sweets with increasing acculturation(Reference Bermudez, Falcon and Tucker10, Reference Hara, Egusa and Yamakido35, Reference Kim and Chan36), but disagree with other results with respect to salt and meat consumption(Reference Nicolaou, van Dam and Stronks32, Reference Montoya, Torres and Torija37, Reference Gilbert and Khokhar38).
Acculturation to the dominant diet appears to occur mainly through the addition of new food items (sugar and sweets) to an existing traditional diet. Moreover, acculturation appears to induce the adoption of French consumer behaviours related to meat consumption. However, this dietary change affected only a few food items and dietary components. Indeed, in spite of a better overall diet quality among Tunisian migrants than their French counterparts, there were few differences between the two groups(Reference Mejean, Traissac, Eymard-Duvernay, El Ati, Delpeuch and Maire16). Not surprisingly, Tunisian migrants and local-born French, all natives of the Mediterranean basin, appear to share certain dietary characteristics.
Influence of past exposure to Tunisian socio-cultural norms
The timing of immigration appears to be important in determining Na intake. Detailed results showed that the lower salt intake among ‘late’ migrants was due to their lower consumption of processed meats, which contain large amounts of Na(Reference Pietinen, Valsta, Hirvonen and Sinkko39). The effect of age at migration on processed meat consumption could be explained by major differences between Tunisia and France with respect to changes in the patterns of consumption of this food group. To our knowledge, there has been no study of Tunisian consumption of processed meats. However, we know that, in Tunisia, meat availability has remained low since 1961, whereas in France there has been a major increase in the consumption of meat, highlighting a clear trend towards a Western diet(Reference Garcia-Closas, Berenguer and Gonzalez40). Moreover, a previous study showed that the Na intake of migrants was lower than that of local-born French and similar to that of non-migrant Tunisians(Reference Mejean, Traissac, Eymard-Duvernay, El Ati, Delpeuch and Maire16). Thus, Tunisian migrants who come to France after the age of 20 may bring with them traditional Tunisian dietary habits (low consumption of processed meats and low Na intake), which do not change much after their arrival, whereas in migrants who come when they are younger, these Tunisian habits may not be so well established because of shorter past exposure to Tunisian socio-cultural norms. Likewise, detailed analysis showed that conservation of the observance of the religious restriction on alcohol consumption was reinforced by longer exposure to the Tunisian context.
Influence of current exposure to Tunisian socio-cultural norms
The present study provides some evidence that current exposure to Tunisian socio-cultural norms can influence the dietary patterns and physical activity levels of Tunisian immigrants currently residing in the South of France. Migrants who were less exposed to the current Tunisian context were less physically active. This lower physical activity level among men who maintained distant ties with the home country was linked to their lower percentage of time spent in occupational activities.
Detailed results showed that the higher MUFA:SFA ratio among migrants who maintained close ties with their home country was due to higher consumption of olive oil. The increase in the consumption of olive oil and fats with increasing strength of social ties with Tunisia could be explained by the current consumption level of this food group in Tunisia. In this country, the olive oil availability was greater than in France, indicating a major difference in eating patterns for this product between the host country and the home country(Reference Garcia-Closas, Berenguer and Gonzalez40). Concerning fat consumption, a previous publication showed that there was no difference between Tunisian migrants, local-born French and non-migrant Tunisians(Reference Mejean, Traissac, Eymard-Duvernay, El Ati, Delpeuch and Maire16). However, the percentage contribution of fats to energy intake has increased greatly in Tunisia in recent decades(Reference Ben Hamida, Fakhfakh, Miladi, Zouari and Nacef41). Migrants who were the most exposed to the current Tunisian context could conserve some dietary habits such as high consumption of olive oil. At the same time, they also could adapt other habits (high fat consumption) alongside the change in eating patterns in their home country.
A feature of our study was the confounding effect between the ‘acculturation’ and ‘exposure to social norms of the home country’ proxies (length of residence, age at migration and social ties with the home country) on dietary characteristics and physical activity. In fact, these three exposure variables were associated with each other (Table 5). Social ties with the home country and length of residence were not fully independent concepts, given that for example the ‘language preference’ item in the index reflecting the current exposure to Tunisian context is also often used as a proxy for acculturation(Reference Satia-Abouta, Patterson, Neuhouser and Elder42, Reference Lin, Bermudez and Tucker43). However, our results showed that the influence of acculturation on outcome variables was not really mediated by current exposure to Tunisian social norms and vice versa, indicating that these proxies were two concomitant but different dimensions that could influence lifestyles. On the other hand, age at migration had a strong confounding effect for the influence of acculturation on many dietary characteristics and physical activity level, whereas this variable only had an independent effect on Na intake. Concerning length of residence, we did find confounding effects for the influence of age at migration on outcome variables and also independent effects of this proxy variable for several dietary variables. Thus, past exposure to the Tunisian context could influence dietary characteristics through acculturation in the new environment.
Relationships between length of residence, age at migration and social ties with the home country: Tunisian migrants, South of France, 2004
As for the specific characteristics of the present study, concerning potential selection bias the non-random nature of the sample may be an issue, but the quota sampling strategy was the only possible solution among migrant populations in France. In addition, the sample size was originally calculated for other purposes, i.e. to compare Tunisian migrants with two non-migrant groups and not to make comparisons within the group of migrants. Also, the cross-sectional study design classically precludes the strict inference of causality regarding the relationship between acculturation and lifestyle changes, which would be better assessed by a longitudinal design(Reference Perez-Escamilla and Putnik9). Furthermore, data collected using FFQ are not as accurate as data gathered using precise recall methods. However, our aim was not to make a comprehensive assessment of dietary intake. Rather, we were mainly interested in comparing the different groups according to length of residence, age at migration and social ties with Tunisia.
In conclusion, Tunisian migrants adopted some French eating habits while maintaining traditional Tunisian eating habits, rather than rejecting either one of them. The present study supports the view that a greater degree of acculturation can lead to a convergence of eating patterns to those of the host population. In addition, our study indicates that past and current exposure to Tunisian socio-cultural norms likely enabled the maintenance of positive aspects of the traditional Tunisian diet (low Na intake and high MUFA:SFA ratio). Thus, our study emphasises the benefit for dietary patterns of preserving food traditions from the country of origin, particularly a traditional Mediterranean diet which has been associated with greater longevity and reduced mortality and morbidity for CHD and certain cancers(Reference Serra-Majem, Roman and Estruch44).
However, along with the rapid nutritional transition in Tunisia(Reference Mokhtar, Elati, Chabir, Bour, Elkari, Schlossman, Caballero and Aguenaou18), these positive aspects could disappear. Indeed, our findings highlighted the fact that, depending on the degree of their current exposure to their home country, Tunisian migrants may modify their traditional diet alongside dietary changes currently underway in Tunisia (fat consumption).
Our work thus suggests that preserving and improving food traditions from the home country and supporting a lifestyle that includes sufficient physical activity should be considered in the development of health promotion activities relating to North African migrant men in France.
Acknowledgements
The study was supported by the Institute of Research for Development (IRD), France. The first author received a research grant from the French Medical Research Foundation (FRM). The authors declare that they have no competing interests.
The authors thank the association CESAM-Migration Health. They also thank the Regional Office for Health and the French National Institute of Statistics for their contribution relating to the survey of migrants in France. They are also grateful to the technicians who helped conduct the survey. Finally, the authors wish to thank all those interviewed in the course of the study for their kindness and their cooperation.
Authors’ contributions: C.M. designed the study, carried out the surveys, performed the statistical analysis and drafted the manuscript. P.T. supervised the statistical analysis and participated in drafting the manuscript. S.E.-D. performed data management and statistical analyses and participated in drafting the manuscript. F.D. was involved in drafting the manuscript and gave his expert comments and suggestions to improve it. B.M. was involved in the conception and design of the study, in the interpretation of data and helped draft the manuscript. All authors have read and approved the final manuscript.
