Disentangling basal and accumulated body mass for cross-population comparisons

Adipose development is consistent across hunter-gatherers and diverges from western references

Despite agreement that humans have evolved to be unusually fat primates, adipose patterning among hunter-gatherers has received little empirical consideration. Here we consider the development of adiposity among four contemporary groups of hunter-gatherers, the Aka, Savanna Pumé, Ju'/Hoansi and Agta using multi-level generalized additive mixed modelling to characterize the growth of tricep skinfolds from early childhood through adolescence. In contrast to references, hunter-gatherers show several consistent patterns: (i) children are lean with little fat accumulation; (ii) no adiposity rebound at 5 years is evident; (iii) girls on average have built 90% of their body size, and reach menarche when adiposity is at its maximum velocity; and (iv) a metabolic trade-off is evident in young, but not older children, such that both boys and girls prioritize skeletal growth during middle childhood, a trade-off that diminishes during adolescence when height velocity increases in pace with fat accumulation. Consistent results across hunter-gatherers living in diverse environments suggest that these patterns reflect a general forager pattern of development. The findings provide a valuable baseline for adipose development not apparent from reference populations. We emphasize both generalized trends among hunter-gatherers, and that inter-populational differences point to the plasticity with which humans organize growth and development.

Association of weight-adjusted waist index with all-cause mortality among non-Asian individuals: a national population-based cohort study

INTRODUCTION

The Weight-Adjusted Waist Index (WWI) is a new indicator of obesity that is associated with all-cause mortality in Asian populations. Our study aimed to investigate the linear and non-linear associations between WWI and all-cause mortality in non-Asian populations in the United States, and whether WWI was superior to traditional obesity indicators as a predictor of all-cause mortality.

METHODS

We conducted a cohort study using data from the 2011-2018 National Health and Nutrition Examination Survey (NHANES), involving 18,592 participants. We utilized Cox proportional hazard models to assess the association between WWI, BMI, WC, and the risk of all-cause mortality, and performed subgroup analyses and interaction tests. We also employed a receiver operating characteristics (ROC) curve study to evaluate the effectiveness of WWI, BMI, and WC in predicting all-cause mortality.

RESULTS

After adjusting for confounders, WWI, BMI, and WC were positively associated with all-cause mortality. The performance of WWI, BMI, and WC in predicting all-cause mortality yielded AUCs of 0.697, 0.524, and 0.562, respectively. The data also revealed a U-shaped relationship between WWI and all-cause mortality. Race and cancer modified the relationship between WWI and all-cause mortality, with the relationship being negatively correlated in African Americans and cancer patients.

CONCLUSIONS

In non-Asian populations in the United States, there is a U-shaped relationship between WWI and all-cause mortality, and WWI outperforms BMI and WC as a predictor of all-cause mortality. These findings may contribute to a better understanding and prediction of the relationship between obesity and mortality, and provide support for effective obesity management strategies.

Assessing comparative asset-based measures of material wealth as predictors of physical growth and mortality

Social scientists and policymakers have increasingly relied on asset-based indices of household wealth to assess social disparities and to identify economically vulnerable populations in low- and middle-income countries. In the last decade, researchers have proposed a number of asset-based measures that permit global comparisons of household wealth across populations in different countries and over time. Each of these measures relies on different assumptions and indicators, and little is known about the relative performance of these measures in assessing disparities. In this study, we assess four comparative, asset-based measures of wealth-the Absolute Wealth Estimate (AWE), the International Wealth Index (IWI), the Comparative Wealth Index (CWI), and the "Standard of Living" portion of the Multi-Dimensional Poverty Index (MPI), along with a variable measuring television ownership-and compare how well each predicts health related variables such as women's BMI, children's height-for-age Z scores, and infant mortality at the household and survey level. Analyzing data from over 300 Demographic and Health surveys in 84 countries (n = 2,304,928 households), we found that AWE, IWI, CWI, MPI are all highly correlated (r = 0.7 to 0.9). However, IWI which is based on a common set of universally weighted indicators, typically best accounts for variation in all three health measures. We discuss the implications of these findings for choosing and interpreting these measures of wealth for different purposes.

One size does not fit all. How universal standards for normal height can hide deprivation and create false paradoxes

Public health practitioners and social scientists frequently compare height against one-size-fits-all standards of human growth to assess well-being, deprivation, and disease risk. However, underlying differences in height can make some naturally tall populations appear well-off by universal standards, even though they live in severe states of deprivation. In this article, I describe the worldwide extent of these population differences in height and illustrate how using a universal yardstick to compare population height can create puzzling disparities (eg, between South Asia and sub-Saharan Africa) while also underestimating childhood stunting in specific world regions (eg, West Africa and Haiti). I conclude by discussing potential challenges of developing and implementing population-sensitive standards for assessing healthy development.

Deprivation or discrimination? Comparing two explanations for the reverse income-obesity gradient in the US and South Korea

In high-income countries, poverty is often associated with higher average body mass index (BMI). To account for this reverse gradient, deprivation theories posit that declining economic resources make it more difficult to maintain a healthy weight. By contrast, discrimination theories argue that anti-fat discrimination in hiring and marriage sorts heavier individuals into lower-income households. This study assesses competing predictions of these theories by examining how household income in representative samples from South Korea (2007-2014, N=20,823) and the US (1999-2014, N=6395) is related to BMI in two key contrasting groups: (1) currently-married and (2) never-married individuals. As expected by anti-fat discrimination in marriage, the reverse gradient is observed among currently-married women but not among never-married women in both countries. Also consistent with past studies no evidence was found for a reverse gradient among men. These findings are consistent with anti-fat discrimination in marriage as a key cause of the reverse gradient and raise serious challenges to deprivation accounts as well as explanations based on anti-fat discrimination in labour markets.

Body mass estimation for circum-Pacific Asian people based on somatometric data

OBJECTIVES

Multiple regression approaches for estimating body mass by somatometry typically use stature and biiliocristal breadth. However, these measures were obtained largely from Europeans, Africans, and Indo-Mediterraneans, whereas mid-latitude Asians were not broadly reflected. Thus, new estimation formulas for circum-Pacific Asians were devised, and the accuracy was evaluated using raw individual data.

MATERIALS AND METHODS

Targeting Asians in the traditional society or before the 1960s and performing multiple regression analysis (MRA) with body weight as the objective variable, and stature, body breadth, and product of head length/breadth (HLBpr) as explanatory variables. The target population was divided into four climate groups, and the formulas were prepared for each sex or the combined-sexes.

RESULTS

The MRA by stature and body breadth indicated significant multiple correlation coefficients (R) in many formulas. R was higher in the combined-sexes. Among the four climate groups, the temperate group showed the highest R. In the East/Southeast Asians, R exceeded 0.8 in the MRA by stature and HLBpr. Substituting the raw data of 19th-century Japanese males, the temperate group formulas presented the least error, and the error in all the formulas using body breadth was <2 kg.

CONCLUSIONS

As body mass index varies significantly depending on some climatic factors, estimation formulas mixed with various climate groups are not desirable because of the large errors. For the mid-latitude Asians, the temperate group formulas are expected to have a smaller error; however, in the group where the proportion of underweight individuals was originally high, any formula tends to be overestimated.

Identifying the limits to socioeconomic influences on human growth

Contemporary humans occupy the widest range of socioeconomic environments in their evolutionary history, and this has revealed unprecedented environmentally-induced plasticity in physical growth. This plasticity also has limits, and identifying those limits can help researchers: (1) parse when population differences arise from environmental inputs or not and (2) determine when it is possible to infer socioeconomic disparities from disparities in body form. To illustrate potential limits to environmental plasticity, we analyze body mass index (BMI) and height data from 1,768,962 women and 207,341 men (20-49 y) living in households exhibiting 1000-fold variation in household wealth (51 countries, 1985-2017, 164 surveys) across four world regions-sub-Saharan Africa, South Asia, Latin America, and North Africa and the Middle East. We find that relationships of environmental inputs with both mean height and BMI bottom out at roughly 100-700 USD per capita household wealth (2011 international units, PPP), but at different basal BMIs and basal heights for different regions. The relationship with resources tops out for BMI at around 20 K-35 K USD for women, with growth potential due to environmental inputs in the range of 6.2-8.4 kg/m². By contrast, mean BMI for men and mean height for both sexes remains sensitive to environmental inputs even at levels far above the low- and middle-income samples studied here. This suggest that further work integrating comparable data from low- and high-income samples should provide a better picture of the full range of environmental inputs on human height and BMI. We conclude by discussing how neglecting such population-specific limits to human growth can lead to erroneous inferences about population differences.

Ancient origins of low lean mass among South Asians and implications for modern type 2 diabetes susceptibility

Living South Asians have low lean tissue mass relative to height, which contributes to their elevated type 2 diabetes susceptibility, particularly when accompanied by obesity. While ongoing lifestyle transitions account for rising obesity, the origins of low lean mass remain unclear. We analysed proxies for lean mass and stature among South Asian skeletons spanning the last 11,000 years (n = 197) to investigate the origins of South Asian low lean mass. Compared with a worldwide sample (n = 2,003), South Asian skeletons indicate low lean mass. Stature-adjusted lean mass increased significantly over time in South Asia, but to a very minor extent (0.04 z-score units per 1,000 years, adjusted R2 = 0.01). In contrast stature decreased sharply when agriculture was adopted. Our results indicate that low lean mass has characterised South Asians since at least the early Holocene and may represent long-term climatic adaptation or neutral variation. This phenotype is therefore unlikely to change extensively in the short term, so other strategies to address increasing non-communicable disease rates must be pursued.

Secondary data analysis to answer questions in human biology

Despite a growing number of publicly available datasets, the use of these datasets for secondary analyses in human biology is less common compared with other fields. Secondary analysis of existing data offers an opportunity for human biologists to ask unique questions through an evolutionary and biocultural lens, allowing for an analysis of cultural and structural nuances that affect health. Leveraging publicly available datasets for human biology research is a way for students and established researchers to complement their data collection, use existing data for master's and doctoral theses, pilot test questions, and use existing data to answer interesting new questions or explore questions at the population level. Here we describe where publicly available data are stored, highlighting some data repositories and how to access them. We then discuss how to decide which dataset is right, depending on the research question. Next, we describe steps to construct datasets, analytical considerations and methodological challenges, best practices, and limitations depending on the structure of the study. We close by highlighting a number of publicly available datasets that have been used by human biologists and other datasets that may be of interest to the community, including research that has been conducted on some example datasets.

Anti-fat discrimination in marriage more clearly explains the poverty-obesity paradox

The target article proposes the insurance hypothesis as an explanation for higher levels of obesity among food-insecure women living in high-income countries. An alternative hypothesis based on anti-fat discrimination in marriage can also account for such correlations between poverty and obesity and is more consistent with finer-grained analyses by marital status, gender, and age.

One size does not fit all: Examining ethnicity in gestational weight gain guidelines

Pregnancy-related metrics vary by race/ethnicity, yet most gestational weight gain (GWG) guidelines are ethnicity-blind. We estimated small-for-gestational age (SGA) risk in a Japanese population, examining GWG adequacy categorized by Institute of Medicine (IOM) and Japanese guidelines in male (N  = 192) and female (N = 191) full-term singleton infants. For predicting SGA, IOM guidelines had high sensitivity ( ≥ 0.75), but low specificity ( ≤ 0.25); Japanese guidelines had high specificity ( ≥ 0.80) but low sensitivity ( ≤ 0.50). GWG guidelines' implicit notions of Caucasian-Americans as optimal may lead to 'One Size Fits All' recommendations that can obscure important biocultural factors contributing to maternal child health outcomes.

Gender empowerment, inequalities and the prevalence of adult female obesity: An empirical analysis using new data, 1990-2013

Aims: Do gender inequality and gender discrimination explain female obesity? Discrimination denies access to choose and constrains agency. Scope: Using the Global Burden of Disease data on overweight and obesity share of the adult female population for almost 160 countries over a 24-year period, we find that female empowerment has no effect on the population share that is overweight, but it reduces the obese share of women. The substantive impact is, however, slight and the results are not robust to testing a sample of only developing countries. Political freedoms for women in general, however, show positive effects on the prevalence of obesity, results that are again substantively meagre. Higher levels of income inequality and a measure of health inequality predict lower levels of female obesity independently of the controls, which raises some doubt about large arguments linking generalized inequality to obesogenic environments. Results: In so far as our measures of female empowerment capture greater access to rights and agency, they are poor predictors of the prevalence of obesity. The results suggest that local-level idiosyncrasies matter a lot more than do macro-level factors. Conclusions: Any conclusion should be treated tentatively given the short temporal domain examined here and uncertainties in the data. While promoting rights and equity for women are still intrinsically valuable and moral, the task of reducing obesity per se may require more targeted public action promoting healthier lifestyles and consumption among vulnerable groups.

The Weight of Things: Understanding African American Women's Perceptions of Health, Body Image, and Attractiveness

Negative attitudes toward being overweight or obese are widespread, and these notions perpetuate into conceptions about one's health. Clinically, being overweight is associated with health problems such as diabetes, hypertension, heart disease, and many other illnesses. African American women, who are generally larger in body size, are a particular target for health interventions. However, these women have resisted the "obesity" label, arguing that dominant measures of health are White norms and oppressive. Through the use of in-depth interviews, this study investigates how African American women understand and experience healthfulness, body image, and barriers to each. Findings show that African American women are ambivalent in their acceptance of dominant markers of health and expressed an almost universal disdain for the thin ideal as a marker of "good" health and a positive body image. Moreover, participants articulated a suspicion of formal medical measurements of obesity.

Estimating body mass and composition from proximal femur dimensions using dual energy x-ray absorptiometry

Body mass prediction from the skeleton most commonly employs femoral head diameter (FHD). However, theoretical predictions and empirical data suggest the relationship between mass and FHD is strongest in young adults, that bone dimensions reflect lean mass better than body or fat mass and that other femoral measurements may be superior. Here, we generate prediction equations for body mass and its components using femoral head, neck and proximal shaft diameters and body composition data derived from dual-energy x-ray absorptiometry (DXA) scans of young adults (n = 155, 77 females and 78 males, mean age 22.7 ± 1.3 years) from the Andhra Pradesh Children and Parents Study, Hyderabad, India. Sex-specific regression of log-transformed data on femoral measurements predicted lean mass with smaller standard errors of estimate (SEEs) than body mass (12-14% and 16-17% respectively), while none of the femoral measurements were significant predictors of fat mass. Subtrochanteric mediolateral shaft diameter gave lower SEEs for lean mass in both sexes and for body mass in males than FHD, while FHD was a better predictor of body mass in women. Our results provide further evidence that lean mass is more closely related to proximal femur dimensions than body or fat mass and that proximal shaft diameter is a better predictor than FHD of lean but not always body mass. The mechanisms underlying these relationships have implications for selecting the most appropriate measurement and reference sample for estimating body or lean mass, which also depend on the question under investigation.

Relationship between body mass, lean mass, fat mass, and limb bone cross-sectional geometry: Implications for estimating body mass and physique from the skeleton

OBJECTIVES

Estimating body mass from skeletal dimensions is widely practiced, but methods for estimating its components (lean and fat mass) are poorly developed. The ability to estimate these characteristics would offer new insights into the evolution of body composition and its variation relative to past and present health. This study investigates the potential of long bone cross-sectional properties as predictors of body, lean, and fat mass.

MATERIALS AND METHODS

Humerus, femur and tibia midshaft cross-sectional properties were measured by peripheral quantitative computed tomography in sample of young adult women (n = 105) characterized by a range of activity levels. Body composition was estimated from bioimpedance analysis.

RESULTS

Lean mass correlated most strongly with both upper and lower limb bone properties (r values up to 0.74), while fat mass showed weak correlations (r ≤ 0.29). Estimation equations generated from tibial midshaft properties indicated that lean mass could be estimated relatively reliably, with some improvement using logged data and including bone length in the models (minimum standard error of estimate = 8.9%). Body mass prediction was less reliable and fat mass only poorly predicted (standard errors of estimate ≥11.9% and >33%, respectively).

DISCUSSION

Lean mass can be predicted more reliably than body mass from limb bone cross-sectional properties. The results highlight the potential for studying evolutionary trends in lean mass from skeletal remains, and have implications for understanding the relationship between bone morphology and body mass or composition.

Obesity, Metabolism, and Aging: A Multiscalar Approach

Obesity contributes to the aging process through the alteration of metabolic pathways evidenced biochemically in the relationship between caloric restriction and longevity. Humans have entered into an era of metabolism and aging entirely unprecedented in their evolution, with a diet that, for many, contains a majority of calories as sugar and yields an expected lifespan of over 80years in industrialized nations. Deeply embedded in the complex issue of obesity are questions of behavior, causality versus correlation, and appropriate models. For example, are primates a better reference than mice for studying metabolic connections between obesity and aging? We consider those issues from the standpoint of life-history theory, especially implications of the interplay of refined sugar and socioeconomic disparities for the future of human health.

Material wealth in 3D: Mapping multiple paths to prosperity in low- and middle- income countries

Material wealth is a key factor shaping human development and well-being. Every year, hundreds of studies in social science and policy fields assess material wealth in low- and middle-income countries assuming that there is a single dimension by which households can move from poverty to prosperity. However, a one-dimensional model may miss important kinds of prosperity, particularly in countries where traditional subsistence-based livelihoods coexist with modern cash economies. Using multiple correspondence analysis to analyze representative household data from six countries-Nepal, Bangladesh, Ethiopia, Kenya, Tanzania and Guatemala-across three world regions, we identify a number of independent dimension of wealth, each with a clear link to locally relevant pathways to success in cash and agricultural economies. In all cases, the first dimension identified by this approach replicates standard one-dimensional estimates and captures success in cash economies. The novel dimensions we identify reflect success in different agricultural sectors and are independently associated with key benchmarks of food security and human growth, such as adult body mass index and child height. The multidimensional models of wealth we describe here provide new opportunities for examining the causes and consequences of wealth inequality that go beyond success in cash economies, for tracing the emergence of hybrid pathways to prosperity, and for assessing how these different pathways to economic success carry different health risks and social opportunities.

Anthropometric indices for non-pregnant women of childbearing age differ widely among four low-middle income populations

Background

Maternal stature and body mass indices (BMI) of non-pregnant women (NPW) of child bearing age are relevant to maternal and offspring health. The objective was to compare anthropometric indices of NPW in four rural communities in low- to low-middle income countries (LMIC).

Methods

Anthropometry and maternal characteristics/household wealth questionnaires were obtained for NPW enrolled in the Women First Preconception Maternal Nutrition Trial. Body mass index (BMI, kg/m²) was calculated. Z-scores were determined using WHO reference data.

Results

A total of 7268 NPW participated in Equateur, DRC (n = 1741); Chimaltenango, Guatemala (n = 1695); North Karnataka, India (n = 1823); and Thatta, Sindh, Pakistan (n = 2009). Mean age was 23 y and mean parity 1.5. Median (P25-P75) height (cm) ranged from 145.5 (142.2–148.9) in Guatemala to 156.0 (152.0–160.0) in DRC. Median weight (kg) ranged from 44.7 (39.9–50.3) in India to 52.7 (46.9–59.8) in Guatemala. Median BMI ranged from 19.4 (17.6–21.9) in India to 24.9 (22.3–28.0) in Guatemala. Percent stunted (<−2SD height for age z-score) ranged from 13.9% in DRC to 80.5% in Guatemala; % underweight (BMI <18.5) ranged from 1.2% in Guatemala to 37.1% in India; % overweight/obese (OW, BMI ≥25.0) ranged from 5.7% in DRC to 49.3% in Guatemala. For all sites, indicators for higher SES and higher age were associated with BMI. Lower SES women were underweight more frequently and higher SES women were OW more frequently at all sites. Younger women tended to be underweight, while older women tended to be OW.

Conclusions

Anthropometric data for NPW varied widely among low-income rural populations in four countries located on three different continents. Global comparisons of anthropometric measurements across sites using standard reference data serve to highlight major differences among populations of low-income rural NPW and assist in evaluating the rationale for and the design of optimal intervention trials.

Trial registration

ClinicalTrials.gov #NCT01883193 (18 June 2013, retrospectively registered)

Measuring material wealth in low-income settings: A conceptual and how-to guide

Although wealth is consistently found to be an important predictor of health and well-being, there remains debate as to the best way to conceptualize and operationalize wealth. In this article, we focus on the measurement of economic resources, which is one among many forms of wealth. We provide an overview of the process of measuring material wealth, including theoretical and conceptual considerations, a how-to guide based on the most common approach to measurement, and a review of important theoretical and empirical questions that remain to be resolved. Throughout, we emphasize considerations particular to the settings in which anthropologists work, and we include variations on common approaches to measuring material wealth that might be better suited to anthropologists' theoretical questions, methodological approaches, and fieldwork settings.

How does variance in fertility change over the demographic transition?

Most work on the human fertility transition has focused on declines in mean fertility. However, understanding changes in the variance of reproductive outcomes can be equally important for evolutionary questions about the heritability of fertility, individual determinants of fertility and changing patterns of reproductive skew. Here, we document how variance in completed fertility among women (45-49 years) differs across 200 surveys in 72 low- to middle-income countries where fertility transitions are currently in progress at various stages. Nearly all (91%) of samples exhibit variance consistent with a Poisson process of fertility, which places systematic, and often severe, theoretical upper bounds on the proportion of variance that can be attributed to individual differences. In contrast to the pattern of total variance, these upper bounds increase from high- to mid-fertility samples, then decline again as samples move from mid to low fertility. Notably, the lowest fertility samples often deviate from a Poisson process. This suggests that as populations move to low fertility their reproduction shifts from a rate-based process to a focus on an ideal number of children. We discuss the implications of these findings for predicting completed fertility from individual-level variables.

Relationships among fat mass, fat-free mass and height in adults: A new method of statistical analysis applied to NHANES data

OBJECTIVES

The positive influence of fat mass (FM) on fat-free mass (FFM) has been quantified previously by various methods involving regression analysis of population data, but some are fundamentally flawed through neglect of the tendency of taller individuals to carry more fat. Differences in FFM due to differences in FM-and not directly related to differences in height-are expressed as ΔFFM/ΔFM, denoted K_F . The main aims were to find a sounder regression-based method of quantifying K_F and simultaneously of estimating mean BMI₀ , the BMI of hypothetical fat-free individuals. Other, related, objectives were to check the linearity of FFM-FM relationships and to quantify the correlation between FM and height.

METHODS

New statistical methods, explored and verified by Monte Carlo simulation, were applied to NHANES data. Regression of height² on FFM and FM produced estimates of mean K_F and indirectly of BMI₀ . Both were then adjusted to allow for variability in K_F around its mean. Its standard deviation was estimated by a novel method.

RESULTS

Relationships between FFM and FM were linear, not semilogarithmic as is sometimes assumed. Mean K_F is similar in Mexican American men and women, but higher in men than women in non-Hispanic European Americans and African Americans. Mean BMI₀ is higher in men than in women. FM correlates more strongly with height than has been found previously.

CONCLUSIONS

A more accurate way of quantifying mean BMI₀ and the dependence of FFM on FM is established that may be easily applied to new and existing population data.

How much do universal anthropometric standards bias the global monitoring of obesity and undernutrition?

Each year, hundreds of articles in population health and nutrition, many in high-profile journals, use standard cutoffs based on weight and height as assessments of obesity and undernutrition. These global efforts to monitor overweight and underweight often rest on the assumption that ethnic differences in underlying body form are sufficiently small to permit universal anthropometric cutoffs for comparing excess and insufficient body fat across populations. However, a century of work in human biological variation suggests that human populations can vary dramatically in underlying body form in a way that may require population-sensitive cutoffs for monitoring. Here, we describe recently developed methods that can provide population-sensitive assessments of both excess and insufficient energy reserves in a wide range of countries. We use this approach to illustrate how worldwide variation in human body form is far more widespread than previously thought, and that it can occur at several geographic scales, including the level of world regions, countries and populations within countries. The findings also suggest that using standard cutoffs that ignore this variation can underestimate current obesity levels in adults by more than 400-500 million while also incorrectly prioritizing high-risk areas for undernutrition in children in key regions around the world.

Why are there race/ethnic differences in adult body mass index-adiposity relationships? A quantitative critical review

Body mass index (BMI) is now the most widely used measure of adiposity on a global scale. Nevertheless, intense discussion centers on the appropriateness of BMI as a phenotypic marker of adiposity across populations differing in race and ethnicity. BMI-adiposity relations appear to vary significantly across race/ethnic groups, but a collective critical analysis of these effects establishing their magnitude and underlying body shape/composition basis is lacking. Accordingly, we systematically review the magnitude of these race-ethnic differences across non-Hispanic (NH) white, NH black and Mexican American adults, their anatomic body composition basis and potential biologically linked mechanisms, using both earlier publications and new analyses from the US National Health and Nutrition Examination Survey. Our collective observations provide a new framework for critically evaluating the quantitative relations between BMI and adiposity across groups differing in race and ethnicity; reveal new insights into BMI as a measure of adiposity across the adult age-span; identify knowledge gaps that can form the basis of future research and create a quantitative foundation for developing BMI-related public health recommendations.

Estimating the absolute wealth of households

Objective

To estimate the absolute wealth of households using data from demographic and health surveys.

Methods

We developed a new metric, the absolute wealth estimate, based on the rank of each surveyed household according to its material assets and the assumed shape of the distribution of wealth among surveyed households. Using data from 156 demographic and health surveys in 66 countries, we calculated absolute wealth estimates for households. We validated the method by comparing the proportion of households defined as poor using our estimates with published World Bank poverty headcounts. We also compared the accuracy of absolute versus relative wealth estimates for the prediction of anthropometric measures.

Findings

The median absolute wealth estimates of 1 403 186 households were 2056 international dollars per capita (interquartile range: 723–6103). The proportion of poor households based on absolute wealth estimates were strongly correlated with World Bank estimates of populations living on less than 2.00 United States dollars per capita per day (R² = 0.84). Absolute wealth estimates were better predictors of anthropometric measures than relative wealth indexes.

Conclusion

Absolute wealth estimates provide new opportunities for comparative research to assess the effects of economic resources on health and human capital, as well as the long-term health consequences of economic change and inequality.

Genetic population structure accounts for contemporary ecogeographic patterns in tropic and subtropic-dwelling humans

Contemporary human populations conform to ecogeographic predictions that animals will become more compact in cooler climates and less compact in warmer ones. However, it remains unclear to what extent this pattern reflects plastic responses to current environments or genetic differences among populations. Analyzing anthropometric surveys of 232,684 children and adults from across 80 ethnolinguistic groups in sub-Saharan Africa, Asia and the Americas, we confirm that body surface-to-volume correlates with contemporary temperature at magnitudes found in more latitudinally diverse samples (Adj. R² = 0.14-0.28). However, far more variation in body surface-to-volume is attributable to genetic population structure (Adj. R² = 0.50-0.74). Moreover, genetic population structure accounts for nearly all of the observed relationship between contemporary temperature and body surface-to-volume among children and adults. Indeed, after controlling for population structure, contemporary temperature accounts for no more than 4% of the variance in body form in these groups. This effect of genetic affinity on body form is also independent of other ecological variables, such as dominant mode of subsistence and household wealth per capita. These findings suggest that the observed fit of human body surface-to-volume with current climate in this sample reflects relatively large effects of existing genetic population structure of contemporary humans compared to plastic response to current environments.