Current Research

Maternal energy metabolism in endurance athletes during pregnancy and postpartum. In pregnancy and postpartum, mothers face increasing energy demands to support fetal growth and lactation. Previous studies have proposed a limit to sustained energy metabolism in humans (~2.5× basal metabolic rate, BMR; kilocalories/day). It is unclear if pregnancy and postpartum, particularly coupled with high levels of physical activity, pushes maternal energy expenditure beyond the metabolic limit. We hypothesize that there is a metabolic limit to maternal energy expenditure, ~2.5× preconception BMR, which is not surpassed by highly active mothers. We expect physiological trade-offs within a limited energy budget impact maternal and fetal health outcomes. We are testing these hypotheses through a prospective cohort study consisting of an endurance athlete cohort, who continued training during their pregnancies and after delivery, and a relatively sedentary non-athlete cohort matched for age and body mass. Manuscripts are in prep.

• Sadhir, S., McGrosky, A., Swanson, Z.S., Tavormina, A., Tomechko, K., & Pontzer, H. (2025). Physical activity and heat stress shape water needs in pregnant endurance athletes. Evolution, Medicine, and Public Health. Special Issue: Evolution of Water Needs, Heat Stress, & Climate Change. eoaf003. https://doi.org/10.1093/emph/eoaf003

Physiological effects of high physical activity during pregnancy and postpartum. We are investigating the molecular (hormone) mechanisms governing a constrained energy budget in varied maternal environments and lifestyles. We hypothesize that there is altered regulation of maternal somatic maintenance, through energy-sparing mechanisms, in pregnancies that experience competing energy demands—such as high physical activity. For an exploratory analysis, we are investigating estradiol (E1G) and progesterone (PdG) concentrations during pregnancy and postpartum in endurance athletes. Data analysis is ongoing.

Maternal energy metabolism and physical activity among Daasanach semi-nomadic pastoralist women in northern Kenya. In subsistence populations, high physical activity workloads are typically maintained throughout pregnancy. Market integration shifts patterns of physical activity, often resembling industrialized populations, with more time allocated to sedentary behavior and less time allocated to physical activity. Daasanach semi-nomadic pastoralists living in arid northern Kenya face lifestyle heterogeneity due to the emergence of a market center. We examine how Daasanach women manage the energetic demands of pregnancy with subsistence labor tasks and how distance to the market is related to variation in energetic demands, physical activity, and coping strategies. This research is undertaken as part of the Daasanach Human Biology Project. Data collection is ongoing.

• Sadhir, S., McGrosky, A., Ford, L. B., Nzunza, R., Wemanya, S. N., Mashaka, H., Kinyanjui, R., Ndiema, E., Braun, D.R., Rosinger, A.Y., & Pontzer, H. (2024). Physical activity and pregnancy norms Among Daasanach semi‐nomadic pastoralist women in Northern Kenya. American Journal of Human Biology, e24174. https://doi.org/10.1002/ajhb.24174

Physical activity patterns and health outcomes during pregnancy. Energy investment in high levels of physical activity likely trades off with energy investment in reproduction to influence fecundity and pregnancy outcomes. U.S. pregnancy guidelines recommend 150 mins/week of exercise for positive pregnancy outcomes, including lower likelihoods of hypertension, excessive gestational weight gain, and macrosomia. We predict that women with higher physical activity will report lower fecundity and a higher incidence of menstrual disorders. We also predict that women with higher physical activity during pregnancy will reduce their activity over gestation, and report lower incidences of gestational metabolic disorders. We implemented two online survey recruiting women to self-report measures of fecundity, physical activity patterns, perceptions of physical activity, and health outcomes during their last pregnancies (n=1088). Data analysis is ongoing.

Reproductive energetics of ruffed and ring-tailed lemurs. Maternal strategies during pregnancy, lactation, and infant dependency differ greatly between primate species, yet energetic costs of these behaviors are not well understood and have rarely been objectively measured. To improve our understanding of energetic costs associated with reproduction, we are investigating total energy expenditure and accelerometry-derived physical activity over gestation, lactation, and weaning in two lemur species of similar body size at the Duke Lemur Center: ring-tailed lemurs (Lemur catta) and ruffed lemurs (Varecia variegata and V. rubra, grouped as Varecia spp. for the purpose of this study). Manuscript is in prep.

Energy availability and fertility across human populations. We reviewed how energetic factors may influence female reproduction and presented an analysis of age at first reproduction and interbirth interval trends across a diverse, global sample representing 44 countries and two natural fertility populations. We found that alongside economic and cultural influences on fertility, women in energy-rich, industrialized populations are capable of greater reproductive output than women in energy-stressed populations.

• Sadhir, S., & Pontzer, H. (2023). Impact of energy availability and physical activity on variation in fertility across human populations. Journal of Physiological Anthropology, 42(1), 1. https://doi.org/10.1186/s40101-023-00318-3

 

Graduate Mentorship of Undergraduate Honors Theses

• Parker, C. H., Sadhir, S., Swanson, Z., McGrosky, A., Hinz, E., Urlacher, S. S., & Pontzer, H. (2023). Effect of influenza vaccination on resting metabolic rate and c-reactive protein concentrations in healthy young adults. PLOS ONE, 18(12), e0295540. https://doi.org/10.1371/journal.pone.0295540
• Klasson, C. L., Sadhir, S., & Pontzer, H. (2022). Daily physical activity is negatively associated with thyroid hormone levels, inflammation, and immune system markers among men and women in the NHANES dataset. PLoS One, 17(7), e0270221. https://doi.org/10.1371/journal.pone.0270221