PEDRO Y EL LOBO

Having described the trends in the obesity epidemic as well as the diversity of US

Hispanic/Latinos, here I will describe the current disparities in obesity and the current

understanding of its underlying causes.

i. Adulthood

Within the US there are striking disparities in obesity prevalence, which are

masked by looking at just overall national estimates as I had done in my description of

the temporal and geographic trends in the obesity epidemic. For example, as of 2010

non-Hispanic/Latino White adults 20 years or older were estimated to have the lowest

age-adjusted prevalence of obesity (34%, civilian non-institutionalized) [2].

Hispanic/Latinos (39%) and non-Hispanic/Latino Black (50%) adults had a higher burden

of obesity. The Hispanic Health and Nutritional Examination Survey in 1982-1984 was

the first to show that the burden of obesity may not be similar across all background

groups of US Hispanic/Latinos [121, 122]. Restricting the 2010 estimates of obesity

prevalence to just Mexican Americans demonstrated a slightly higher proportion were

obese for this background group than overall for Hispanic/Latinos (40%). More recent

nationally-representative estimates of obesity across the US Hispanic/Latino

backgrounds are currently lacking.

In this regard, community-based studies, like HCHS/SOL, may be a helpful

snapshot of heterogeneity in the burden of obesity in US Hispanic/Latinos. In the

HCHS/SOL communities a slightly smaller proportion of Hispanic/Latinos were obese

(37%) than in contemporary national estimates [6]. Yet the burden of obesity across

Hispanic/Latino backgrounds was indeed highly variable—with South American (27%) and Puerto Rican (41%) adults representing the ends of the spectrum in obesity

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part, to the confounding by geography mentioned above of Hispanic/Latinos in the US

[42, 43].

ii. Childhood and Adolescence

Unfortunately obesity disparities are even more pronounced among US

Hispanic/Latino children and adolescents than in adults [2, 3]. Whereas in 2010 14% of

non-Hispanic/Latino White children and adolescents (2-19 years) were obese, a higher

burden of obesity was shouldered by Hispanic/Latino (21%) and non-Hispanic/Latino

Black (24%) children and adolescents. Although considering all of childhood and

adolescence it appears that the prevalence of obesity in Mexican Americans is similar to

the large Hispanic/Latino designation, an alarming trend towards obesity can be seen in

particular among Mexican American adolescent boys (12-19 years). This observation is

supported by recent work in the National Longitudinal Study of Adolescent Health, which

among the Hispanic/Latino backgrounds saw the largest gains in BMI between 12-32

years in adolescents of Mexican (males) or Puerto Rican (females) ancestry or heritage

[123]. Adolescents of Central/South American, Cuban or other backgrounds gained body

mass at or below the non-Hispanic/Latino White adolescents in the study.

iii. Non-Genetic Determinants of Obesity

This brings us to the question of what might be key underlying determinants of

obesity disparities for US Hispanic/Latinos, as well as what are potential sources of

heterogeneity across this ethnic group’s diverse backgrounds. One possible component is the high proportion of Hispanic/Latinos who do not have health insurance and

therefore affordable access to health care services [124, 125]. Although the Affordable

Healthcare Act was enacted to equalize access to health care in the US, it does not

include undocumented immigrants who are estimated to collectively amount to more

marginalize this vulnerable population [105]. In 2010, 34% of all US Hispanics <65 years

of age did not have health insurance and 45% of US Hispanic/Latinos in families earning

<200% of the poverty line were uninsured [126]. At the same time 14% of non-Hispanic

Whites and 21% of non-Hispanic Blacks were uninsured. Lack of insurance varies

substantially by Hispanic/Latino background groups (e.g. from 50% of Hondurans to

15% of Puerto Ricans were uninsured in 2010) [127], and tends to be highest among

background groups that have the highest proportions of undocumented immigrants such

as immigrants from Mexico (34%) and Central America (41-50%) [103, 127]. When

lacking adequate clinical monitoring and management in roughly half of all US

Hispanic/Latinos <65 years old [124, 126], inequitably some individuals may be

subjected to an array of adverse environmental and lifestyle factors as they assimilate to

the US resulting in poor population-level health outcomes [44]. A systematic review of

mortality disparities in US Hispanic/Latinos (as compared to the general US population)

revealed that although the greatest disparity is seen in diabetes-related mortality,

Hispanic/Latinos also suffer from mortality disparities in a number of other conditions

including some cancers, liver disease, HIV, homicide, and work-related injuries [125].

Diversity across Hispanic/Latino background groups may related to barriers to health

care (e.g. citizenship or legal resident requirements for Medicaid/Medicare and

Affordable Care Act, type and location of employment opportunities, language

preference) and result in both lower seeking and receipt of healthcare services among

Hispanic/Latinos.

Another determinant of the obesity epidemic and the observed disparities relates

to the social determinants of health, which can include poverty, trauma, stress,

discrimination, unskilled or unreliable employment [125]. These health determinants

have been linked to allostatic loads and hypothesized by Marmot to relate to a ‘status syndrome’, characterized by lower participation in and sense of control over their

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surroundings [128]. Low socioeconomic status (SES) has been linked to rates of obesity,

metabolic syndrome, and mortality [125].

Additionally, the sociocultural environment and an individual’s strategy of acculturation [9, 84] may be key determinants in the patterning of diet, physical activity,

obesity disparities. In the absence of the time and the resources to measure

acculturation using detailed scales, proxies of acculturation have become common in

epidemiologic studies of Hispanic/Latinos [9, 83]. In a systematic review of the public

health literature by Thomson and Hoffman-Goetz, nearly a third of studies of

Hispanic/Latinos relied on one or a combination of proxies of acculturation (language

preference, nativity, time in the US, language preference, etc.). The need to balance

practicality with validity is important to the study of the effects of acculturation. According

to their review of the literature when both proxies of acculturation and detailed scales

have been assessed in the same study, the correlations varied across the scales

(r=0.17-0.76).

A number of cross-sectional studies have investigated acculturation and obesity

among US Hispanics/Latinos and have shown positive associations between

acculturation and measures of adiposity, which vary by background [122, 129-138]. In

the cross-sectional literature on this topic, time living in the US is a consistent cross-

sectional predictor of increasing weight status, independent of age, and shows evidence

of a threshold effect after 10 years in the US [8]. A number of other measures of

acculturation, such as age at immigration, generational status, language preference at

examination, nativity, and the Short Acculturation Scale for Hispanics, have previously

shown the most acculturated Hispanic/Latinos to carry the largest obesity burden;

however, the results from studies using these measures have generally been less

These cross-sectional studies have led to a number of competing hypotheses

about the underlying pathway between acculturation and obesity. Hispanic/Latino

immigrants have been documented to be healthier than their US-born peers, in what has

been described as the ‘healthy immigrant effect.’ Explanations of this pattern are similar to the ‘Hispanic paradox’ described above [125] and have revolved in part around the selective migration of the healthiest individuals from the sending countries as well as

retention of protective cultural practices such as a healthier diet and physically active

lifestyle [86, 139]. Others have pointed out that return migration due to immigration

enforcement, retirement, or health concerns (i.e. ‘salmon bias’) [125] may create a reverse selection bias that could mask or accentuate observed differences between

foreign- and US-born Hispanic/Latinos in cross-sectional and longitudinal studies alike

[140, 141].

‘Social adaptation’ provides another alternative explanation of disparities and has been cast in both a positive and negative light in the current literature [125]. In contrast

the ‘unhealthy assimilation’ hypothesis has been posited as an explanation for the cross- sectional observation of the effect of increasing duration in the US [138, 141, 142]. If

recent Hispanic/Latino immigrants are exposed to obesogenic environments as they

assimilate to the US then they would gain weight faster than native-born

Hispanic/Latinos until their weights converged. In a more positive light, ‘divergence’ describes the possibility that more recent immigrants may be more likely to maintain

cultural practices, which support healthy lifestyles with regards to diet and physical

activity, as they negotiate the process of establishing new relationships in the US.

A handful of longitudinal studies [142-145] and repeated cross-sectional studies

[140, 141] (Table 1) have sought to test the hypotheses of an ‘healthy immigrant effect’ followed by ‘unhealthy assimilation’ to the US by testing for baseline differences in obesity by generational status and then assessing the rates of weight gain between

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foreign- and US-born Hispanic/Latinos. However, the findings have been far more mixed

than seen previously in the cross-sectional literature [122, 129-138].

Within the body of literature some studies have noted incomplete mediation of

the cross-sectional [139, 146, 147] or longitudinal [148] effect of acculturation on obesity

by diet or physical activity, which may indicate that other sociocultural or environmental

factors other than diet or physical activity may mediate the influence of acculturation

(assimilation to US society) on obesity [8, 147]. Specifically, the association may be

mediated by coping strategies for the stress related to immigration, discrimination, or

other characteristic of being Hispanic/Latino in the US [149]. Other researchers propose

that ‘segmented’ (unequal) assimilation [150] or structural factors not captured by the individual concept of acculturation [90] may in turn compromise the health of certain

segments of the Hispanic/Latino population [145].

In summary restricted or inconsistent access to health care or SES disadvantage

may interact with geographic, Hispanic/Latino background, immigration status, linguistic,

sociocultural and ancestral diversity to determine the patterning of obesogenic

environments in the US. This could in turn yield the complex picture of Hispanic/Latino

health and health disparities in obesity we see currently in the US [2, 125].