Body composition helps: Differences in energy expenditure between pregnant and nonpregnant females

Abstract

Objectives: Human pregnancy is associated with important physiological changes that usually increase energetic requirements. However, great variability exists in the costs and mechanisms required to bear pregnancy. Since body mass (BM) and composition are modified during gestation, it is of great interest to compare the influence of BM on energy expenditure (EE) in pregnant and nonpregnant females.Methods: BM, body composition, and EE of 77 volunteers (35 pregnant and 42 nonpregnant females) were measured. The pregnant volunteers completed two measurement rounds at 28 and 32 gestation weeks. Differences on the measured parameters were sought, and comparison of regression lines was computed to test how BM affected the EE of the volunteers.Results: BM and body composition parameters are significantly higher in pregnant females, but EE is not statistically different. Pregnant females have a larger percentage of fat mass, but lower percentage of fat-free mass (FFM). The EE per kg of FFM is similar in both groups. Comparison of regression lines shows that pregnancy does not change the relationship between BM and EE, but for similar BM pregnant females expend less energy than nonpregnant females. Conclusions: We propose that their larger percentage of passive body tissues is the reason why pregnant females expend less energy than nonpregnant females of similar BM, without changing the scaling of EE on BM. Thus, pregnancy could not be as energetically constraining as usually assumed, with important consequences for human reproductive ecology.

EVOBREATH. Datasets for evolutionary bioenergetics research on anthropology

“…These data are also required to understand the evolutionary ecophysiological constraints of hominin past populations. Some of the raw data recorded in these datasets were analysed in a number of original research articles [1] , [2] , [3] , [4] , [5] , [6] , [7] , [8] , [9] , [10] .…”

At their own pace: Optimal walking speed in children and adolescents

“…Conversely, females walking in groups tend to walk closer to their optimal speed, minimizing their own energetic costs. It has been proposed that within hunter‐gatherer societies, this energy saving strategy allowed females to allocate a greater amount of energy to reproduction, load transport, and infant carriage (Kramer, 1998; Bouterse & Wall‐Scheffler, 2018; Wall‐Scheffler & Myers, 2013; but see also Prado‐Nóvoa et al, 2021). One strategy to deal with this energetic burden for the faster individuals in a group or in a dyad is to set up the group's composition by gender when traveling longer distances or when performing daily energetically intensive tasks.…”