Abstract
Background:
Overweight/obesity (OW/OB) coexists in mother–child dyads. However, a dearth of evidence on the factors associated with this phenomenon calls for research.
Objective:
To analyze the association of sociodemographic factors with OW/OB in a sample of 260 Maya mother–child dyads from Yucatan, Mexico.
Methods:
During 2011 to 2014, we measured height and weight in children and their mothers and calculated their body mass index (BMI). The OW/OB cutoff points were defined, for mothers, as having a BMI >25 kg/m2 and, for children, as having a BMI-for-age >2 standard deviation of the World Health Organization references. Mother–child dyads were grouped according to their BMI status: (1) normal weight mother and child, (2) normal weight mother and OW/OB child, (3) OW/OB mother and normal weight child, and (4) OW/OB mother and child. A multinomial logistic regression model was used to analyze the interrelationships among BMI status in mother–child dyads, household size, and parental education.
Results:
Overweight/obesity coexisted in 40% of dyads. Compared to normal weight dyads (1), each unit increase in household size and in years of maternal education decreased the risks of the coexistence of OW/OB in mother–child dyads (odds ratio [OR] = 0.72, 95% confidence interval [CI] 0.55-0.94, P = .015; OR = 0.70, 95% CI 0.52-0.94, P = .019, respectively). Conversely, each year increase in paternal education increased the risk for OW/OB in dyads (OR = 1.47, 95% CI 1.08-1.99, P = .015).
Conclusions:
Results suggest that household size and parental education contribute to shape BMI-based nutritional status in this sample of mother–child dyads.
Introduction
Globally, minority ethnic groups face higher risk of negative health and well-being outcomes than privileged groups. 1,2 In Latin America and the Caribbean (LAC) countries, infant and maternal morbidity and mortality tend to be higher in minority ethnic groups due to several factors including discrimination, socioeconomic disadvantages, poor living conditions, and limited access to health services. 2,3 Changes in the epidemiological profiles observed in LAC countries show clear increases in the prevalence of noncommunicable diseases associated with obesity. 4 Overweight and obesity (OW/OB) are chronic health conditions that carry high economic burden for individuals, families, and communities. 5 It is expected that these costs will be greater in minority ethnic groups due to their higher levels of material poverty and limited access to social security coverage.
Mexico has the largest number of inhabitants belonging to any indigenous groups in LAC countries. 3 The Maya represents the second largest ethnic group in Mexico, 6 and the Yucatan Peninsula of Mexico is the home of around 787 500 Maya people who reside in both urban and rural areas. 7 Historically, the classical Maya had been widely recognized and valued by their significant advances in mathematics, astronomy, architecture, and agriculture. 8 However, most of the living Maya nowadays face poverty and deprivation and do not reap any benefit from their heritage. Most of the Maya population from Yucatan is integrated into a global economy of labor and consumption, while a small proportion of them depends on traditional agricultural systems for subsistence. 9
Available studies on nutritional status of urban Maya population from Yucatan show very high rates of OW/OB in children and adult women. 10,11 Several economic and political factors, including lack of economic support for agricultural activities in rural settings and the imposition of government policies relating to the national and global economy, have urged a large number of Maya people to opt for very low-paid jobs in urban centers such as Merida, the capital city of Yucatan. 12 This process has profoundly influenced food consumption and physical activity patterns among the Maya, increasing their susceptibility to OW/OB and other chronic diseases. 13,14
Overnutrition can be studied at individual, mother–child pair, familial, and population levels. Mothers and their children are in closer contact and share more time and food environments than other members of the family, and, therefore, similarities in body weight status are expected among them. 15 The study of mother–child dyads as a unit of analysis provides a useful scenario to investigate the influence of living conditions and of intergenerational effects on health and nutritional aspects of some of the most vulnerable members of minority groups.
The combination of BMI and weight outcomes, when analyzing in mother–child dyads, can be seen in relation to different correlates that vary in terms of social, economic, biological, and health-related issues. The coexistence of OW/OB represents a scenario with social, economic, and health costs for families and population. So far, these different outcomes in combinations have not been studied in depth. Many studies have analyzed the impact of the dual burden of malnutrition at the household level, in which maternal OW/OB coexists with childhood stunting. 16 -18 This is a familial phenotype that is frequently seen in low- and middle-income countries that are undergoing nutrition transition. However, OW/OB in mother–child dyads usually means that the nutrition transition has been experienced, and phenotypes of these populations resemble the phenomenon observed in high-imcome countries where the epidemic of OW/OB has been prevalent.
In this study we aim to analyze the association of sociodemographic factors, namely, household size and parental education, with the presence or absence of concomitant OW/OB in a sample of 260 Maya mother–child dyads residing in the cities of Merida and Motul in Yucatan, Mexico.
Methods
The data set used in the present study was part of a research project on the influence of socioeconomic and intergenerational factors on growth and nutritional status of 6- to 8-year old Maya children from the cities of Merida and Motul in Yucatan, Mexico. The research was cross-sectional in nature and aimed to analyze how living conditions experienced by mothers and maternal grandmothers during their childhood had associations with growth and body composition characteristics of children in the younger generation. Inclusion criteria were based on (1) age of children (6.00-8.99 years), (2) the mother was the biological mother of child, and (3) each member of the triad (maternal grandmother, mother, and child) had to have at least 1 maternal Maya surname. In Mexico, people use both patronymic and matronymic surnames that can be considered as a genetic proxy and a means to identify ethnic affinity. 19 -21 We focused on 6- to 8-year-old children because during this stage skeletal growth rate tends to be stable or decelerating, and there are few skeletal maturation differences between boys and girls. 22 In this study, we focus on anthropometric characteristics of mothers and their children in the background of selected household sociodemographic factors. The sample consisted of 260 mother–child dyads from Merida (n1 = 180) and Motul (n2 = 80).
Merida, located in the north–central region of the Yucatan Peninsula, is the capital city of Yucatan state. In 2015, Merida was inhabited by 892 363 people, 11% of them being Maya speakers. The presence of Maya people in Merida has long history; however, during the last decades, the city has become an increasingly important destination for rural-to-urban Maya migrants. Maya people residing in Merida work mostly in construction, manufacturing, domestic, commercial, transport, and other services as low-wage employees. 12 Motul is located around 30 km away from Merida in the north–central region of the state. In 2016, Motul was inhabited by 36 097 people, 25% of them being Maya speakers. The higher proportion of Maya people living in this city in comparison with Merida is partially explained by the presence of haciendas (treasury of the landholders) in Motul neighborhood, where Maya people worked as laborers in the production of sisal fiber (Agave flouricoides) in 19th and 20th centuries. The current labor market in Motul primarily consists of small-scale agriculture and livestock, commerce, manufacturing operations (maquiladoras), and tourism.
Data Collection
From September 2011 to January 2014, we conducted a cross-sectional study in which we measured height and weight of children and their mothers and calculated their body mass index (BMI = weight [kg]/height [m2]). During the duration of the project, 3 sessions of anthropometric standardization were implemented in which only <5% of interobserver technical error of measurement was acceptable. Children were measured in schools between 7 and 10
Mother–child dyads from Merida were recruited from 47 primary schools located in several regions of the city. In order to allow for greater socioeconomic variability in the sample, we randomly selected 10 participants from each school. Dyads from Motul were recruited from 12 primary schools of the city.
Overweight/obesity cutoff points (OW/OB) were defined, for the mothers, as having BMI >25 kg/m2 and, for the children, as having a BMI-for-age above 2 SD of the WHO references. 25 Mother–child dyads were grouped into 4 categories according to OW/OB and normal weight conditions: (1) normal weight mother–normal weight child, (2) normal weight mother–OW/OB child, (3) OW/OB mother–normal weight child and, (4) OW/OB mother—OW/OB child.
During household visits, we used a questionnaire to record data of household socioeconomic characteristics. For the purposes of this study, the variables of interest were household size and parental education. The socioeconomic conditions in Maya families improve as the household size decreases, and this indicator can be related to the distribution and accessibility of resources. Household size was defined as the total number of people living permanently in the house. In this sample, household size ranged from 2 to 13 members. Parental education has been shown to be positively associated with child growth and nutritional status, 26,27 and evidence suggest that effects of parents’ education effect are larger in poor socioeconomic settings and in populations with high burden of malnutrition, 27 such as the Maya. We included education of the mother and the father, since both have been shown to be important for offspring health. 28 Parents’ education levels were recorded in years. For descriptive purposes, data were grouped into 3 categories: (1) none, (2) primary school, (3) junior high school, (4) senior high school, and (5) professional degrees (university and technical education).
Statistical Analyses
Student’s t test was used to find significant differences of mean values between 2 groups. χ2 tests were used to compare the proportions of OW/OB between groups. A logistic regression model was also used to estimate the odds of being OW/OB in children, given the presence or absence of OW/OB in mothers. A multinomial regression model was used to analyze the interrelationships between sociodemographic factors and BMI-based nutritional status in mother–child dyads. Household size and parent’s education (years) were used as predictors. Maternal and children’s age (both in years) and sex (1 = boys, 2 = girls) were used as covariates in the model. Since a small number of dyads fall in the category of normal weight mother–OW/OB child (n = 9), the outcome variable was restricted in this analysis into 3 categories: (1) normal weight mother–normal weight child, (2) OW/OB mother–normal weight child, and (3) OW/OB mother–OW/OB child. The category of normal weight mother–normal weight child was used as the reference in the model. We report the odds ratio (OR), standard error, 95% confidence interval (CI), and P value for each predictor. Statistical analyses were done using the Stata/IC 11.1 for Windows statistical package. Significance level in all analyses was α = .05.
Ethical Concerns
This research project was approved by the Bioethics Committee for the Study of Human Beings of the Centre for Research and Advanced Studies of the National Polytechnic Institute of Mexico and the Loughborough University Ethics Advisory Group (R11-P133). Mothers signed the consent forms for themselves and also on behalf of their children. All children provided us with verbal assent while measured. For ethical reasons, adult women were measured only by women of the research team.
Results
We found no significant differences in anthropometric and sociodemographic data between participants from Merida and Motul. Therefore, results are based on the pooled sample from the 2 cities.
Sociodemographic Characteristics
Participants belong to relatively large families (mean = 5.10, standard deviation [SD] = 1.88) with low levels of parental education being 33% of below primary school (Table 1). No significant differences were identified either in years of education or in the proportions of education levels between mothers and fathers.
Sociodemographic Characteristics of Studied Households.
Abbreviation: SD, standard deviation.
Nutritional Status of Mother–Child Dyads
On average, children’s BMI-for-age Z-score values were 1 SD above the mean of the WHO references. The mean value for mother’s BMI was close to the upper limit of overweight category according to the WHO criteria (Table 2). A large proportion of children (43.90%) and mothers (85.80%) met the criteria for OW/OB. No significant difference was observed in the proportions of OW/OB children by sex (boys = 45.45% vs girls = 42.19%, χ2(1) = 0.282, P > .05). No participant in this study met the criteria for being underweight. Regarding the combinations of nutritional status of mothers and children, the highest percentage of dyads (46%) was found in the category of OW/OB mother and normal weight child, followed by OW/OB mother and child (40%), normal weight dyads (10%), and normal weight mother and OW/OB child (4%). These frequencies did not vary significantly according to children’s sex (χ2 (2) = 0.544, P > .05).
Descriptive Statistics of Anthropometric and Derived Variables of Mothers and Children.
Abbreviations: BMI, body mass index; OW/OB, overweight/obesity; SD, standard deviation.
aOverweight/obesity cutoff points were defined, for the mothers, as having a BMI >25kg/m2 and, for the children, as having a BMI-for-age >2SD of the World Health Organization references. None of the mother or child met the criteria for low BMI or underweight (adults: BMI <18 kg/m2; children <−2SD in BMI-for-age).
We observed that higher proportions of OW/OB children were clustered in the group of OW/OB mothers (47% vs 25%, respectively). Logistic regression analysis showed that being an OW/OB mother more than doubled the odds of children to be classified as OW/OB (odds ratio [OR] = 2.65, 95% CI 1.16-5.80).
Factors Associated With Nutritional Status of Mother–Child Dyads
Multinomial regression analysis (Table 3) showed that, compared to the normal weight dyads, each unit increase in household size, and in years of maternal education, decreased the odds for the presence of OW/OB in mothers and children (OR = 0.72, 95% CI 0.55-0.94, P = .015; OR = 0.70, 95% CI 0.52-0.94, P = .019). This implies children and mothers are less likely to be OW/OB if they live in bigger houses and if the mothers report higher educational qualifications. Conversely, each year increase in father’s education also increased the odds for the presence of OW/OB in members of both generations (OR = 1.47, 95% CI 1.08-1.99, P = .015). No predictor included in the model was found to be significantly associated with the category of OW/OB mother and normal weight child.
Multinomial Regression Model for Categories of BMI Status in Mother–Child Dyads.a
Abbreviations: CI, confidence interval; OR, odds ratio; OW/OB, overweight/obesity.
aThe category normal weight mother–OW/OB child was not included given the small number of cases (n = 9).
Discussion
In summary, our results show that excess body weight coexists in 40% of mother–child dyads. Our analysis shows that household size and years of maternal education were negatively associated with the risk of OW/OB in mother–child dyads, and conversely, fathers’ education increased the risk for the presence of OW/OB in mothers and children.
The 43.9% of children in the sample met the criteria for high BMI-for-age, which is greater compared to national prevalence (34.6%) and similar to that found in Yucatan state (45.2%), according to the 2012 Mexican National Survey of Health and Nutrition. 29 The prevalence of OW/OB in the mothers was 12.8% and 4% greater than national and Yucatan figures (National = 73%, Yucatan = 82%), respectively. Previous studies from Yucatan reported that children and youth with Maya ancestry or individuals belonging to disadvantaged socioeconomic groups tend show poorer growth status, including increased risk of excess body weight. 30,31 In this sense, Ulijaszek proposes that societies characterized by strong economic and social gradations tend to produce unequal manifestations of diseases. Ethnic groups that occupy the lowest rank in terms of wealth and societal position are especially impacted upon. 32
Despite the recognition of the importance of mother–child dyads as a useful approach to obtain valuable information that could enable improvements in health status of populations, very limited data about the prevalence of the coexistence of excess body weight in mother–child pairs are available. In their study on geographic relationships of nutritional status as measured by BMI among Kenyan mothers and children (3 to 5 years of age), Pawloski and collaborators 33 found that the most frequent category was normal weight mother–normal weight child (49.3%), followed by OW/OB mother–normal weight child (14.8%). Only 5.7% Kenyan dyads, mostly clustered in urban areas of the country, showed the coexistence of excess body weight, a prevalence substantially lower than that found in our Maya sample.
In general, it is expected that the coexistence of excess body weight in mothers and offspring increases if the frequency of OW/OB rises separately in adult women and children. Despite this, no other study to the best of our knowledge has analyzed factors associated with OW/OB in mother–child pairs. Therefore, results of this study contribute to the limited discussion about the influence of intrahousehold-level factors on nutritional status of Maya families from Yucatan, Mexico. We found that households with fewer members showed an increased risk of having OW/OB in mothers and their children. As reported earlier, 34 living conditions of urban Maya families improve as household size decreases, which allows us to expect a negative association between household size and the risk of excess body weight in dyads that might be explained by a larger amount of foods and type of care to each member as the household size decreases. This finding is consistent with previous studies done in poor socioeconomic setings. 35,36 Our results also show that mother–child dyads are less likely to be OW/OB if the mothers have more years of education and more likely if the fathers report higher educational qualification. It has been proposed that parental education acts as an indicator of children’s health through 2 interrelated lanes. First, higher education may cause changes in parental values, which is related to household income and allocation of resources towards children’s and parents’ health awareness. Second, more years of schooling may improve cognitive skills, facilitating increased household income and health awareness. 37 Most of the mothers in the studied sample are not engaged in regular salaried jobs and are responsible of the daily household chores and child care. Therefore, we may suggest that maternal education acts through decisions related to food selection and preparation inside the household. In this regard, evidence suggests that the association of dietary practices between parents and children tends to be stronger in mother–child dyads than fathers. 38 We suggest that father’s education acts through household income, and higher paternal income may cause a greater access to overall amount of food. These results are consistent with McLaren’s review 39 in the sense that in countries with medium and low Human Development Index (a measure of national development based on people and economic growth), obesity is positively associated with higher levels of education among men but negatively in women. In the case of children, available studies suggest that inequalities experienced by parents, but particularly by mothers, can shape rates of OW/OB among their offspring. 40,41 Therefore, it is possible that the coexistence of excess body weight observed in 40% of dyads are explained by a complex interaction of factors, including a relatively greater capacity for food purchasing, the selection of products with high caloric content, and the distribution of resources among a small number of members in the household.
Nutritional status of adult women and children of the present study may have several implications not only for the population but also for health personnel. We think the coexistence of excess body weight in mother–child dyads may tend to normalize the presence of unhealthy weights at household and community levels and therefore undersestimate their detrimental consequences of obesity on health and well-being. Normalization of OW/OB may prevent successful actions of practitioners and researchers when they try to make behavioral changes in diet and physical activity or focus on obesity prevention.
We presume that current nutritional status of the Maya might be also explained by factors at macro-level. Briefly, the Maya exemplify sociodemographic changes recently experienced by other ethnic groups. Until the end of 19th century, a large proportion of Maya people resided in rural areas in the context of the hacienda system and in communities as small-scale farmers. 42 Traditional Maya diets and their living conditions presumed a high-energy expenditure due to long and exhausting working hours. Due to several factors such as the deterioration in soil fertility, lack of government support for agriculture, and the fall of the agro-industrial system of sisal, a considerable number of Maya people migrated to the main cities of the Yucatan. 12,43 The urban dynamics transformed the sociodemographic and cultural characteristics of the Maya. National policies related to birth control have contributed to a substantial reduction in the size of the families. The labor dynamics based on salaried work has modestly increased the income of families and therefore their purchasing capacity. In this context, the urban Maya have been exposed to a food supply characterized by a diverse range of products of low cost but nutritionally poor, where local elements of the traditional diet were replaced by the commercially produced foods. 44
Finally, our results show the urgent need for action at different levels to improve the health conditions of the Maya population. As a fundamental principle, it is essential that living conditions of the Maya improve and that needs active policy measures designed by the government, such as regular access to education, especially for girls.
Limitations
Limitations of our research include the lack of information that could help us to better understand the studied phenomenon. First, we lack data about participants’ diet and physical activity levels, factors that could influence individual prevalences of OW/OB and thereby the combinations of these conditions in mother–child dyads. Second, we also lack data about other relevant characteristics of the parents and household that could explain the coexistence of OW/OB among dyads, including household income, food expenditure, and maternal perceptions about their own body shape and that of their children.
In conclusion, excess body weight is a widespread condition in this sample of Maya mothers and their children, and parental years of schooling and household size contribute to shape the coexistence of this condition in mother–child dyads. The results call for an urgent need for interventions at different levels in the Maya population.
Footnotes
Authors’ Note
This study derives substantially from the Master’s thesis of Paulina Cauich-Viñas under the supervision of Hugo Azcorra. Paulina Viñas-Cauich and Hugo Azcorra formulated the research question and wrote the first draft of the manuscript. Hugo Azcorra and Luis Rodríguez analysed the data. Federico Dickinson, Sudip Datta Banik, and Maria Ines Varela-Silva contributed to the creative process of this article by providing scientific content and intellectual additions on the subsequent drafts of the manuscript.
Acknowledgments
The authors thank those who assisted with the field work: Graciela Valentín Sánchez and Adriana Vázquez-Vázquez. Additional fieldwork assistance was provided by Frida Gutiérrez and Samantha Sánchez. We appreciate the cooperation of mothers and their children who agreed to participate in the study.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: The data reported here were collected as part of a project funded by the National Science and Technology Council of Mexico; Consejo Nacional de Ciencia y Tecnología de México (Conacyt). Contract grant number: 168047.
