Obesity in International Migrant Populations

Unraveling common threads in obesity risk among racial/ethnic minority and migrant populations

BACKGROUND

Epidemic obesity poses a major threat to global health. This phenomenon reflects the inability of the average person to cope, biologically and behaviorally, with environmental contexts that promote caloric overconsumption and inadequate caloric expenditure. There is still much to be learned about how to improve these contexts nationally and within-countries for sociodemographic groups with above-average obesity risks.

METHODS

Higher obesity risks relative to respective white majority populations were identified among diverse indigenous, other native-born, or migrant 'racial' or ethnic minority (hereafter, ethnic minority) populations in the United States, Canada, Australia, New Zealand, and the Netherlands, using publicly available national survey data or other sources. Cross-national comparisons were of interest for identifying common risk pathways associated with social and economic inequities. Potential explanations were explored through a narrative review of peer-reviewed literature, informed by the World Health Organization's Conceptual Framework for Action on The Social Determinants of Health.

MAIN FINDINGS

Identifying viable solutions to the high risk of obesity in ethnic minority populations in these high-income countries requires examination of national-level social, economic, and health system contexts, food systems, and built environments for physical activity, as well as patterns of social stratification and cultural biases related to ethnicity, migration, and other determinants of social disadvantage. These factors can be linked to mediators of exposure or vulnerability to obesity-related risks, such as poverty, being an 'outsider', stress and trauma resulting from historical and current oppression, exposure to bias and discrimination, related biological or behavioral consequences, and inadequate health and social care.

CONCLUSIONS

Focusing on ethnic minority populations in high-income countries is critical for public health efforts to address epidemic obesity. Mitigating intersecting risk pathways arising from stratification and bias based on ethnicity and migrant status should be prominent in these efforts.

'The hunger trap hypothesis': New horizons in understanding the control of food intake

The global obesity epidemic continues to present significant challenges to individuals and healthcare providers. Public health initiatives to tackle the rise in overweight and obesity in developed and developing nations have largely failed to tackle the problem and research into the underlying causes is of increasing importance. Central to understanding overconsumption of calories is an appreciation of the mechanisms of hunger and satiety. Research to date has revealed considerable detail regarding meal size, macronutrient composition of the diet and control of energy balance via adipose store derived signalling. It is clear however that such control mechanisms are overwhelmed in a significant proportion of the population. We hypothesize the hitherto under-researched possibility that micronutrient status may have an important role in energy balance. Poor vitamin and mineral profiles in the diets of the obese may potentiate overconsumption of calories due to an insufficiency of micronutrient intake relative to macronutrient consumption, a situation aggravated by increased requirements in the obese state. Amongst the multiplicity of metabolic and biochemical processes dependent upon micronutrients and which are impacted by their relative insufficiency, there may be triggers for increased food consumption in an attempt to bridge the gap between high energy consumption and low co-factor availability. This 'hunger trap' will continue as long as low nutrient density foods represent the mainstay of the diet. The accepted paradigm of variety seeking leading to vitamin and mineral adequacy of diets may not apply in the context of highly processed foods which use technological means to mimic organoleptic properties of nutrient density without delivering the same at the level of metabolism.

Effect of high-fat diet-induced obesity on the small-conductance Ca2+-activated K+ channel function affecting the contractility of rat detrusor smooth muscle

PURPOSE

Obesity usually induces overactive bladder (OAB) associated with detrusor overactivity, which is related to increased contractility of the detrusor smooth muscle (DSM). Small-conductance Ca²⁺-activated K⁺ (SK) channels play a constitutive role in the regulation of DSM contractility. However, the role of SK channels in the DSM changes in obesity-related OAB is still unknown. Here, we tested the hypothesis that obesity-related OAB is associated with reduced expression and activity of SK channels in DSM and that SK channels activation is a potential treatment for OAB.

METHODS

Female Sprague-Dawley rats were fed a normal diet (ND) or a high-fat diet (HFD) and weighed after 12 weeks. Urodynamic studies, quantitative reverse transcription-polymerase chain reaction (qRT-PCR), and isometric tension recording were performed.

RESULTS

Increased average body weights and urodynamically demonstrated OAB were observed in HFD rats. qRT-PCR experiments revealed a decrease in the mRNA expression level of SK channel in DSM tissue of the HFD rats. Isometric tension recordings indicated an attenuated relaxation effect of NS309 on the spontaneous phasic and electrical field stimulation-induced contractions that occurred via SK channel activation in HFD DSM strips.

CONCLUSIONS

Reduced expression and activity of SK channels in the DSM contribute to obesity-related OAB, indicating that SK channels are a potential therapeutic target for OAB.

A US/Mexico Study of Joint Associations of Physical Activity and Sedentary Behavior on Anthropometric Indicators, Migration Status, Country of Birth and Country of Residence

Background: This study examined the influence of migration status, nativity and country of residence on joint associations of physical activity (PA) and sedentary behavior (SB) in anthropometric indicators of Mexicans and Mexican-Americans living in the US and in Mexico. Methods: We examined data from two large national surveys, the National Health and Nutrition Examination Survey from the US (NHANES, 2011–2012) and Mexico (ENSANUT, 2012). Using self-reported minutes of moderate to vigorous physical activity and SB, we calculated four categories for analyses. Anthropometric measures consisted of body mass index (BMI) and waist circumference (WC). We used data of migration status, nativity and country of residence. Linear regression models examined how joint categories of PA and SB were associated with BMI and WC according to migration status, nativity and country of residence, controlling for health risk behaviors. Results: Analyses showed that even among those in the category with the lowest risk behavior, “physically active and low sedentary”, there were differences in BMI and WC by migration status, nativity and country of residence. Within this lower risk category, Mexican immigrants living in the US had the greatest association with high BMI, while US-born Mexican-Americans living in the US had the highest WC values when compared with the group of Mexicans living in Mexico. Conclusions: Joint categories of PA and SB were associated with BMI and WC by migration status, nativity and country of residence among populations with Mexican ethnicity.

Exploring the diet and lifestyle changes contributing to weight gain among Australian West African women following migration: A qualitative study

AIMS AND OBJECTIVES

This paper reports on women's experiences of weight gain and obesity as they became acculturated to the Australian diet and lifestyle.

BACKGROUND

Migrants from sub-Saharan Africa have a much higher risk of obesity than the native population when settling in industrialised countries.

METHOD

Qualitative.

RESULTS

Women in this study reported weight gain post-migration. This was attributed to increased access to a wide variety of food including takeaway food and more sedentary lifestyles.

CONCLUSIONS

Obesity has long-term consequences for health and well-being. Further research is needed to support a healthy transition to life in Australia.

RELEVANCE TO CLINICAL PRACTICE

Gaining insight into the underlying reasons that West African immigrants to Australia become obese could contribute to assisting health professionals design culturally appropriate interventions and health education programmes to support new arrivals.

Genetic architecture: the shape of the genetic contribution to human traits and disease

Genetic architecture describes the characteristics of genetic variation that are responsible for heritable phenotypic variability. It depends on the number of genetic variants affecting a trait, their frequencies in the population, the magnitude of their effects and their interactions with each other and the environment. Defining the genetic architecture of a complex trait or disease is central to the scientific and clinical goals of human genetics, which are to understand disease aetiology and aid in disease screening, diagnosis, prognosis and therapy. Recent technological advances have enabled genome-wide association studies and emerging next-generation sequencing studies to begin to decipher the nature of the heritable contribution to traits and disease. Here, we describe the types of genetic architecture that have been observed, how architecture can be measured and why an improved understanding of genetic architecture is central to future advances in the field.