Sex differences in adipose development in a hunter‐gatherer population

Abstract

Objective Humans are unusually sexually dimorphic in body composition, with adult females having on average nearly twice the fat mass as males. The development of adipose sex differences has been well characterized for children growing up in food‐abundant environments, with less known about cross‐cultural variation, particularly in populations without exposure to market foods, mechanized technologies, schooling, vaccination, or other medical interventions. Methods To add to the existing cross‐cultural data, we fit multiple growth curves to body composition and anthropometric data to describe adipose development for the Savanna Pumé, South American hunter‐gatherers. Results (1) Little evidence is found for an adiposity ‘rebound’ at the end of early childhood among either Savanna Pumé girls or boys. (2) Rather, fat deposition fluctuates during childhood, from age ~4 to ~9 years, with no appreciable accumulation until the onset of puberty, a pattern also observed among Congo Baka hunter‐gatherers. (3) Body fat fluctuations are more pronounced for girls than boys. (4) The age of peak skeletal, weight, and adipose gains are staggered to a much greater extent among the Savanna Pumé compared to the National Health and Nutrition Examination Survey (NHANES III) reference, suggesting this is an important developmental strategy in lean populations. Conclusion Documenting growth patterns under diverse preindustrial energetic conditions provides an important baseline for understanding sex differences in body fat emerging today under food abundance.

Development of adiposity among Ju/’Hoansi Hunter‐Gatherers

“…Published results for adiposity as part of childhood growth and development among hunter‐gatherers are limited to the Baka pygmies of the Congo (Rozzi et al, 2015), and the Savanna Pume’ of Venezuela (Kramer et al, 2022). The Baka, however, have known alterations in the IGF‐1axis (Jarvis et al, 2012; Little, 2020), which affects height development and may influence the pattern of adipose development.…”

“…As a sensitivity check, curves also were fit using both a penalized spline (Suk et al 2019) and a loess smoothed curve, which were compared to those best‐fit polynomial models. Both the penalized beta spline and loess smoothed curves were produced by running a series of models with increasingly sensitive smoothing parameters and selecting the best‐fit models using AIC comparisons (Kramer et al, 2022).…”

“…In contrast, results from the Savanna Pume’ foragers of Venezuela, based on multiple curve fitting methods, demonstrate a transient rise in tricep skinfolds during middle childhood for boys and girls coupled with a pre‐pubertal nadir and subsequent pubertal increase (Kramer et al, 2022). Among the Baka of the Congo, the other foraging population for which fine‐grained data are available, visual inspection of age‐related changes in tricep skinfolds (Rozzi et al, 2015), reveals a similar lack of an adipose rebound along with a pre‐pubertal nadir (Kramer et al, 2022). Together these two studies suggest that hunter‐gatherer groups more generally may lack an adiposity rebound starting around 5–6 years.…”

Drought, psychosocial stress, and ecogeographical patterning: Tibial growth and body shape in Samburu (Kenyan) pastoralist children

“…Sex differences in adiposity are well known, although there are fewer studies in young children (Orsso et al, 2020): U.S. girls have been found to have slightly more fat at birth (assessing infant body composition using air displacement plethysmography) (Davis et al, 2019); and Pumé girls have been found to have more peripheral fat (triceps skinfold thickness) in childhood than boys (Kramer et al, 2021). Based on an overview paper, adipose tissue at birth and infancy has a persisting influence on adiposity in childhood and adolescence (Orsso et al, 2020).…”

“…Leroy and colleagues (2015) offer a mathematical explanation for age‐dependent patterns in linear growth. Regarding skinfold thicknesses specifically, Kramer et al emphasize the appropriateness of NHANES III as it is “the last known available collection of skinfold and arm circumference measurements predating the recent obesity trend in children, and has the advantage of all growth metrics being from the same cohort of children” (Kramer et al, 2021, p4). Since our purpose is comparative within a population (see also Kramer et al, 2021), we have used z ‐scores derived from NHANES III for all children in the sample.…”