Obesity is not just elevated adiposity, it is also a state of metabolic perturbation

Nettle et al. miss the crucial difference between adaptive models of storing energy and explanations for the pathological metabolic state of obesity. I suggest that the association of food insecurity with obesity in women from industrialized settings is most likely due to reverse causation: Poverty reduces agency to resist obesogenic foods, and this scenario is compounded by perturbations of insulin metabolism stemming from high adiposity and lipogenic diets

Body composition and susceptibility to Type 2 Diabetes: an evolutionary perspective

Type 2 diabetes is rapidly increasing in prevalence worldwide, in concert with epidemics of obesity and sedentary behavior that are themselves tracking economic development. Within this broad pattern, susceptibility to diabetes varies substantially in association with ethnicity and nutritional exposures through the life-course. An evolutionary perspective may help understand why humans are so prone to this condition in modern environments, and why this risk is unequally distributed. A simple conceptual model treats diabetes risk as the function of two interacting traits, namely ‘metabolic capacity’ which promotes glucose homeostasis, and ‘metabolic load’ which challenges glucose homoeostasis. This conceptual model helps understand how long-term and more recent trends in body composition can be considered to have shaped variability in diabetes risk. Hominin evolution appears to have continued a broader trend evident in primates, towards lower levels of muscularity. In addition, hominins developed higher levels of body fatness, especially in females in relative terms. These traits most likely evolved as part of a broader reorganization of human life history traits in response to growing levels of ecological instability, enabling both survival during tough periods and reproduction during bountiful periods. Since the emergence of Homo sapiens, populations have diverged in body composition in association with geographical setting and local ecological stresses. These long-term trends in both metabolic capacity and adiposity help explain the overall susceptibility of humans to diabetes in ways that are similar to, and exacerbated by, the effects of nutritional exposures during the life-course

A trade-off between cognitive and physical performance, with relative preservation of brain function

Debate surrounds the issue of how the large, metabolically expensive brains of Homo sapiens can be energetically afforded. At the evolutionary level, decreased investment in muscularity, adiposity and the digestive tract allow for a larger brain. Developmentally, high neo-natal adiposity and preferential distribution of resources to the brain provide an energetic buffer during times of environmental stress. Through an experimental design, we investigated the hypothesis of a trade-off involving brain and muscle at the acute level in humans. Mental performance was measured by a free-recall test, and physical performance by power output on an indoor rowing ergometer. Sixty-two male student rowers performed the two tests in isolation, and then again simultaneously. Paired samples t-tests revealed that both power output and mental performance reduced when tested together compared to in isolation (t(61) = 9.699, p < 0.001 and t(61) = 8.975, p < 0.001). Furthermore, the decrease in physical performance was greater than the decrease in mental performance (t(61) = −2.069, p = 0.043). This is the first investigation to demonstrate an acute level trade-off between these two functions, and provides support for the selfish brain hypothesis due to the relative preservation of cognitive function over physical power output. The underlying mechanism is unclear, and requires further work

Evaluation of air-displacement plethysmography in children aged 5-7 years using a three-component model of body composition

The aim of the present study was to evaluate air-displacement plethysmography (ADP) in children aged 5-7 years. Body-composition measurements were obtained by ADP, H-2 dilution and anthropometry in twenty-eight children. Calculation of body volume by ADP was undertaken using adult and children's equations for predicting lung volume and surface area. Fat-free mass (FFM) was calculated using a three-component model. Measured FFM hydration was then compared with values from the reference child. Differences between measured and reference hydration were back-extrapolated, to calculate the error in ADP that would account for any disagreement. Propagation of error was used to distinguish the contributions of methodological precision and biological variability to total hydration variability. The use of children's equations influenced the results for lung volume but not surface area. The mean difference between measured and reference hydration was 0.6 (SD 1.7) % (P<0.10), equivalent to an error in body volume of 0.04 (So 0.20) litres (P<0.30), and in percentage fat of 0.4 (SD 1.9) (P<0.28). The limits of agreement in individuals could be attributed to methodological precision and biological variability in hydration. It is concluded that accuracy of ADP was high for the whole group, with a mean bias of <0.5% fat using the three-component model, and after taking into account biological variability in hydration, the limits of agreement were around 2 % fat in individuals. Paediatric rather than adult equations for lung volume estimation should be used

Weight centile crossing in infancy: correlations between successive months show evidence of growth feedback and an infant-child growth transition

Background: Early rapid weight gain is associated with later overweight, which implies that weight centile crossing tracks over time. Objective: Centile crossing is defined in terms of the change or deviation in weight z score during 1 mo, and the correlations between successive deviations are explored at different ages. Design: Two Cambridge (United Kingdom) growth cohorts were used: Widdowson (1094 infants born during 1959–1965) and the Cambridge Infant Growth Study (CIGS; 255 infants born during 1984–1987), each with weights measured monthly in the first year. Weights were converted to WHO age- and sex-adjusted z scores, deviations were calculated as the change in z score between adjacent measurement occasions, and the correlations between deviations were studied. Results: In both cohorts, the correlations between successive monthly deviations were positive in the first 6 mo and highest at ages 3–4 mo (r = 0.3, P < 0.0001), whereas after 6 mo they were negative and were lowest at ages 10–11 mo (r = –0.3, P < 0.0001), with the correlation decreasing linearly with age between these extremes. Thus, during the first 6 mo of age, infants crossing centiles in 1 mo tended to continue crossing centiles in the same direction the following month, whereas after 6 mo they tended to cross back again. This represents positive and negative feedback, respectively. At age 12 mo, the correlation was close to zero, which suggests an infant-child transition in growth. Conclusions: The results confirm that weight centile crossing tracks over time, with the correlations between successive periods that change with age suggesting a complex feedback mechanism underlying infant growth. This may throw light on the link between early rapid weight gain and later overweight. Clinically, the correlations indicate that when predicting future weight from current weight, recent centile crossing affects the prediction in an age-dependent manner

Associations of gender inequality with child malnutrition and mortality across 96 countries.

National efforts to reduce low birth weight (LBW) and child malnutrition and mortality prioritise economic growth. However, this may be ineffective, while rising gross domestic product (GDP) also imposes health costs, such as obesity and non-communicable disease. There is a need to identify other potential routes for improving child health. We investigated associations of the Gender Inequality Index (GII), a national marker of women's disadvantages in reproductive health, empowerment and labour market participation, with the prevalence of LBW, child malnutrition (stunting and wasting) and mortality under 5 years in 96 countries, adjusting for national GDP. The GII displaced GDP as a predictor of LBW, explaining 36% of the variance. Independent of GDP, the GII explained 10% of the variance in wasting and stunting and 41% of the variance in child mortality. Simulations indicated that reducing GII could lead to major reductions in LBW, child malnutrition and mortality in low- and middle-income countries. Independent of national wealth, reducing women's disempowerment relative to men may reduce LBW and promote child nutritional status and survival. Longitudinal studies are now needed to evaluate the impact of efforts to reduce societal gender inequality.This is the final version of the article. It first appeared from Cambridge University Press via http://dx.doi.org/10.1017/gheg.2016.

First-Borns Carry a Higher Metabolic Risk in Early Adulthood: Evidence from a Prospective Cohort Study

Background: Birth order has been associated with early growth variability and subsequent increased adiposity, but the consequent effects of increased fat mass on metabolic risk during adulthood have not been assessed. We aimed to quantify the metabolic risk in young adulthood of being first-born relative to those born second or subsequently.Methodology and Principal Findings: Body composition and metabolic risk were assessed in 2,249 men, aged 17-19 years, from a birth cohort in southern Brazil. Metabolic risk was assessed using a composite z-score integrating standardized measurements of blood pressure, total cholesterol, high density lipoprotein, triglycerides and fat mass. First-borns had lower birth weight z-score (Delta = -0.25, 95%CI -0.35, -0.15, p<0.001) but showed greater weight gain during infancy (change in weight z-score from birth to 20 months: Delta = 0.39, 95%CI 0.28-0.50, P<0.0001) and had greater mean height (Delta = 1.2 cm, 95%CI: 0.7-1.6, p<0.0001) and weight (Delta = 0.34 kg, 95%CI: 0.13-0.55, p<0.002) at 43 months. This greater weight and height tracked into early adulthood, with first-borns being significantly taller, heavier and with significantly higher fat mass than later-borns. The metabolic risk z-score was significantly higher in first-borns.Conclusions/Significance: First-born status is associated with significantly elevated adiposity and metabolic risk in young adult men in Brazil. Our results, linking cardiovascular risk with life history variables, suggest that metabolic risk may be associated with the worldwide trend to smaller family size and it may interact with changes in behavioural or environmental risk factors

Relationships of Maternal and Paternal Anthropometry With Neonatal Body Size, Proportions and Adiposity in an Australian Cohort

The patterns of association between maternal or paternal and neonatal phenotype may offer insight into how neonatal characteristics are shaped by evolutionary processes, such as conflicting parental interests in fetal investment and obstetric constraints. Paternal interests are theoretically served by maximizing fetal growth, and maternal interests by managing investment in current and future offspring, but whether paternal and maternal influences act on different components of overall size is unknown. We tested whether parents' prepregnancy height and body mass index (BMI) were related to neonatal anthropometry (birthweight, head circumference, absolute and proportional limb segment and trunk lengths, subcutaneous fat) among 1,041 Australian neonates using stepwise linear regression. Maternal and paternal height and maternal BMI were associated with birthweight. Paternal height related to offspring forearm and lower leg lengths, maternal height and BMI to neonatal head circumference, and maternal BMI to offspring adiposity. Principal components analysis identified three components of variability reflecting neonatal “head and trunk skeletal size,” “adiposity,” and “limb lengths.” Regression analyses of the component scores supported the associations of head and trunk size or adiposity with maternal anthropometry, and limb lengths with paternal anthropometry. Our results suggest that while neonatal fatness reflects environmental conditions (maternal physiology), head circumference and limb and trunk lengths show differing associations with parental anthropometry. These patterns may reflect genetics, parental imprinting and environmental influences in a manner consistent with parental conflicts of interest. Paternal height may relate to neonatal limb length as a means of increasing fetal growth without exacerbating the risk of obstetric complications. Am J Phys Anthropol 156:625–636, 2015. © 2014 The Authors American Journal of Physical Anthropology Published by Wiley Periodicals, Inc

Could consanguineous marriage provide a cultural alleviation for the obstetric dilemma?

In placental mammals, a poor fit between the physical dimensions of the fetus and maternal pelvis increases the likelihood of obstructed labour. This problem is especially relevant to humans, as our species demonstrates both unique adaptations in pelvic shape and structure associated with bipedalism, and fetal encephalization. Natural selection is expected to have favoured adaptations that reduce the chances of such mismatch within individual mother-offspring dyads. Here, I hypothesise that the cultural practice of consanguineous marriage may have been favoured, on account of increasing the genetic similarity between mothers and offspring and hence the correlation between maternal and fetal physical dimensions. These benefits could be amplified if consanguineous marriage was accompanied by assortative mating for height. An additional benefit of consanguineous marriage for childbirth is the slight reduction in birth size of such offspring compared to non-consanguineous unions. Although the offspring of consanguineous unions have elevated risks of morbidity and mortality, these risks are moderate and the practice could still have been favoured by selection if the reduction in maternal mortality was greater than the increased mortality among individual offspring. This hypothesis could be tested directly by investigating whether rates of obstructed labour are lower in individuals and populations practising consanguineous marriage. At a broader level, phylogenetic analysis could be conducted to test whether consanguineous marriage appears to have originated in the areas where intensive agriculture was first practiced, as adult height typically fell in such populations, potentially exacerbating the risk of obstructed labour

Double burden of malnutrition in thin children and adolescents: low weight does not protect against cardiometabolic risk

If the global epidemic of non-communicable disease (NCD) has a single defining marker, it is seemingly the relentless global increase in body mass index (BMI). At the population level, an increased prevalence of people with high BMI tends to indicate not only higher levels of harmful body fat, but also exposure to other NCD risk factors, such as lipogenenic diets and sedentary behaviour. Within recent decades, the global prevalence of low BMI in adults has steadily fallen, whereas that of high BMI, reflecting obesity, has systematically increased in most countries. Increasingly, rising BMI is observed in younger age groups too, though rates of child undernutrition remain higher than in adults [1]