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

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

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]

Body composition of children with moderate and severe undernutrition and after treatment: a narrative review

BACKGROUND: Until recently, undernourished children were usually assessed using simple anthropometric measurements, which provide global assessments of nutritional status. There is increasing interest in obtaining more direct data on body composition to assess the effects of undernutrition on fat-free mass (FFM) and its constituents, such as muscle and organs, and on fat mass (FM) and its regional distribution. MAIN TEXT: Recent studies show that severe-acute undernutrition, categorised as 'wasting', is associated with major deficits in both FFM and FM that may persist in the long-term. Fat distribution appears more central, but this is more associated with the loss of peripheral fat than with the elevation of central fat. Chronic undernutrition, categorised as 'stunting', is associated with deficits in FFM and in specific components, such as organ size. However, the magnitude of these deficits is reduced, or - in some cases - disappears, after adjustment for height. This suggests that FFM is largely reduced in proportion to linear growth. Stunted children vary in their FM - in some cases remaining thin throughout childhood, but in other cases developing higher levels of FM. The causes of this heterogeneity remain unclear. Several different pathways may underlie longitudinal associations between early stunting and later body composition. Importantly, recent studies suggest that short children are not at risk of excess fat deposition in the short term when given nutritional supplementation. CONCLUSION: The short- and long-term functional significance of FFM and FM for survival, physical capacity and non-communicable disease risk means that both tissues merit further attention in research on child undernutrition

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

Using Body Composition Assessment to Evaluate the Double Burden of Malnutrition

BACKGROUND: Populations in low- and middle-income countries are increasingly experiencing a double burden of malnutrition (DBM), incorporating both persistent levels of child undernutrition and rising prevalence of overweight/obesity at later ages. A growing number of individuals experience both components of the DBM through the life-course, thereby accumulating high susceptibility to noncommunicable disease (NCD). SUMMARY: Measurements of body composition may prove valuable for assessing NCD risk at the level of the individual. The capacity-load model provides a simple conceptual framework for integrating data on different components of body composition to predict NCD risk. Poor growth in early life, indexed by becoming wasted or stunted, constrains the development of lean mass components such as muscle and organ mass, each of which contribute to the metabolic capacity for homeostasis. Catch-up weight gain in early life, or the development of excess weight from childhood onwards, is associated with elevated adiposity, especially abdominal adiposity, which challenges cardio-metabolic homeostasis and elevates NCD risk. Key Messages: A variety of techniques are now available for the measurement of body composition, helping research the association of the DBM with NCD risk. Reference charts allow raw data to be converted to age- and sex-specific z-scores, aiding interpretation

Pregnancies in Diabetes and Obesity: The Capacity-Load Model of Placental Adaptation

Excess nutritional supply to the growing fetus, resulting from maternal diabetes and obesity, is associated with increased risks of fetal maldevelopment and adverse metabolic conditions in postnatal life. The placenta, interposed between mother and fetus, serves as the gateway between the two circulations and is usually considered to mediate maternal exposures to the fetus through a direct supply line. In this Perspective, however, we argue that the placenta is not an innocent bystander and mounts responses to fetal “signals of distress” to sustain its own adequate function and protect the fetus. We describe several types of protection that the placenta can offer the fetus against maternal metabolic perturbations and offer a theoretical model of how the placenta responds to the intrauterine environment in maternal diabetes and obesity to stabilize the fetal environment. Our approach supports growing calls for early screening and control of pregnancy metabolism to minimize harmful fetal outcomes

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

Breast-feeding as 'personalized nutrition'

Health benefits of breast-feeding have been recognised since antiquity [1], and yet with every passing decade, our scientific understanding of breast-feeding as a mode of nutrition seems to accelerate rather than reach a ‘final plateau’. We already have compelling evidence that it matters, yet we also have much to discover about how exactly breast-feeding functions as a biological process, how and why it varies between mother–infant dyads, and what this means for promoting successful breast-feeding to the benefit of mothers and infants. Breast-feeding is arguably the ultimate ‘biosocial’ trait, simultaneously linking complex physiological processes with multiple components of behaviour in both mother and offspring that are amenable to cultural influences [2]