The focus of this paper was to review the research among migrants on the relationship between obesity and acculturation/enculturation as measured by valid and comparable acculturation scales (uni-dimensional and bi-dimensional scales). Only nine studies met the criteria of this review, and all of them were US-based. With the exception of Miller et al. [53
] and Khan et al. [51
], all of the studies reviewed reported generally similar findings indicating an overall positive correlation between acculturation and overweight/obesity. Barcenas et al. [46
] and Ahluwalia et al. [45
] established positive correlations between acculturation and obesity in Mexican-Americans. The more acculturated the populations were, the higher the average BMI. While Khan et al. [51
] found a negative relationship between BMI and acculturation in first-generation migrants, Mexican-Americans’ BMI increased with each generation in the US. Positive relationships between acculturation and obesity were also evident in the studies by Bertera et al. [47
], Fitzgerald et al. [48
], Franzen et al. [49
] and Lee et al. [52
] spanning a wide array of ethnicities (El Salvador, Puerto Rican, Hmong, Korean respectively). However, the relationship appeared more complex for women than for men, as both negative and positive relationships between acculturation and obesity were found for women [50
These findings are likely to also be related to the nutritional transition
documented in developing countries [54
]. Nutritional transition relates to the tendency of decreased consumption of healthy and nutritional foods in favour of fatty and processed foods, observed among citizens in rapidly developing countries [55
]. This effect has been detected globally as unhealthy processed foods are increasingly made available throughout the world [55
]. A good example of this transition is Brazil where, since the 1970s, the problems of dietary deficiency have been replaced by those of dietary excess [56
]. This nutrition transition would occur more rapidly in a migrating population as they make the transition over months and years as opposed to a whole country making the transition over years and decades. The nutrition transition for immigrants thus involves both the qualitative change in diet and the rapidity of that change which would be accentuated in migrants from low- and middle-income countries to high-income countries [55
Looking beyond the overall tendencies in the relationship between obesity and acculturation, however, the relationship becomes more complex and appears to vary by gender, country of origin and SES. In some cases acculturation even seems to predict positive behaviour such as increased physical activity [46
] and decreased CVD-risk and waist-circumference [53
]. Specifically, Khan et al. [51
], and Hazuda et al. [50
], found protective effects of acculturation in terms of female body weight – that is, an inverse correlation between female BMI and acculturation was apparent in these studies in spite of the overall positive association between BMI and acculturation. Similar findings were evident in Miller et al. [53
] study on female Soviet Union immigrants to the US. Of further relevance in this context, it is important to note that while Lee et al. [52
] observed positive correlations between acculturation and body weight, this association held true only for men and not for women. Together, these studies thus lend credence to the idea of gender as a moderating variable in the relationship between acculturation/enculturation and obesity.
Despite the small number of publications, potential explanatory hypotheses can be developed for these emerging patterns. For the females in some migrating populations, it may be that as they get wealthier, the more health conscious they become, which in turn is reflected in behaviour and BMI. Such an effect has been documented for the relationship between SES and BMI where this association is positive until a certain level of wealth is reached after which the correlation inverts [57
]. This flip in the relationship is much stronger for women than for men, and thus could account for the variability in results concerning female subgroups discussed in this review [57
The counteracting environments and social norms in Western countries may have a differential impact on the migrating population depending on migrant country of origin, gender and SES [59
]. The recurring finding that women with higher levels of acculturation have lower BMIs suggests that greater availability of fatty and processed foods in high income countries may be offset by the Western social norms and fashions which endorse fitness, health and a slim body shape [61
]. This is supported in the study by Ahluwalia et al. [45
] where it was established that obese Mexican-Americans with a low degree of acculturation were more satisfied with their weight and body shape, and less likely to have tried to lose weight than their highly acculturated counterparts. Further, Barcenas et al. [46
] and Lee, et al. [52
] found that in spite of a comparatively higher likelihood of increased BMI in acculturated men and women, this cohort was also more likely to engage in physical exercise than non-acculturated participants. These findings appear to highlight a possible association between acculturation and both adaptive and maladaptive health behaviours endorsing health ideals, such as physical activity and slenderness, as well as
facilitating obesogenic habits.
Strengths and limitations
A strength of this review relates to the chief goal of the paper which was to identify and review the research which has used valid and comparable acculturation scales to measure the relationship between acculturation and obesity in migrants to high-income countries. While only nine studies met the inclusion criteria for this paper, the fact that all of the reviewed research employed acculturation scales in their methodology effectively facilitated comparison and synthesis of the main themes and variations emanating from this research. This has not been done before and has thus far represented a gap in the literature on this topic. Nonetheless, although the studies included in our review used validated acculturation scales they varied in terms of number of items and domains covered. For example, some studies [45
] included one dimension that focused on language acculturation rather than a broader array of behaviours related to the migration and settlement process. Others included questions regarding language use and preference, social connections, and overall eating patterns [49
], while others still focused on functional integration (i.e. adoption of the values, attitudes, and behaviour of the host society) [50
], structural acculturation [52
], and language, identity, and behaviour [53
]. In addition, when examining the relationship between acculturation and obesity, some studies used self-reported BMI measures whereas other used measured BMI, making it difficult to draw conclusions across studies. Thus, the variation in acculturation domains and measurement identified in this review emphasises the urgent need for a standardized international acculturation scale.
Another strength of this review centres on the broader research methodology of the included studies. Eight of them employed a cross-sectional design. While the correlational nature of this methodology prohibits a statistical assessment of cause and effect, it can be more readily applied to large representative samples as well as take into account a number of potentially confounding factors. Further, given the specific nature of the variables measured in the reviewed studies, it is still possible to hypothesise with relative certainty on the direction of the associations found despite the nature of cross-sectional research designs. That is, it is much more likely that acculturation has an impact on body weight than vice versa, and while several other factors may mediate or moderate the relationship, this direction of the association remains the most plausible.
A major limitation to the review, relates to the fact that all of the studies focussed on immigrants in the US – a country which is among the ten most obese nations in the world [64
]. In light of this, it is conceivable that obesity may not be related to acculturation in general, but rather to the specific culture to which immigrants acculturate. That is, immigration and acculturation to a country where obesity is not a prominent health issue may not increase migrant BMI. More research examining immigration to countries other than the US is therefore needed for more generalisable conclusions.
Another limitation relates to acculturation scales used. The introduction to this study identified the bi-directional model of acculturation as being more complex and sophisticated than the uni-dimensional model. The current review included studies which used both types of scales, making it difficult to compare specific results across these studies using a common metric. There is also some debate focusing on socioeconomic status and its possible role on the relationship between acculturation and obesity. However, not all the nine studies took this into account and therefore lack of adequate control for SES perhaps partly explain the distinct findings among women.
Finally, the review included studies which used both measured and self-reported BMI (Barcenas et al., 2007; Lee et al., 2000). This comprises a limitation as the accuracy of self-reported BMIs may be questionable.