Female Adolescent Energy Expenditure in the Gambia

Adolescence is a life history transition of individual and evolutionary importance: the body begins to allocate energy available above maintenance costs away from somatic growth and towards reproductive function. This study investigates how both distal, intergenerational effects and proximal, seasonal changes in energy availability impact the way adolescent female bodies allocate energy among linear growth, fat and lean mass, activity, and metabolic function. The research follows up on a prenatal supplementation study conducted by the British Medical Research Council in rural Gambia between 1989 and 1994. Pregnant women were randomized to receive daily supplements of 1015 kcal either from week 20 of pregnancy until delivery or during the first 20 weeks of lactation. The 67 adolescent daughters included in the follow up study were born to women in both groups during the rainy agricultural season, the period of the year associated with weight loss, poor perinatal outcomes, and high impact of the pregnancy supplement on birth weight. Anthropometry, body composition, daily saliva, weekly serum, and weekly fasting urine samples for C-peptide of insulin were collected during one month each in the 2009 rainy agricultural season, the 2010 dry harvest season, and the 2010 rainy agricultural season. Participant heart rates were calibrated to oxygen consumption each season, and 24-hr accelerometer and heart rate data were recorded to estimate free-living energy expenditure. It was found that pregnancy supplementation status did not predict infant or adolescent phenotype in the study sample. Maternal postpartum weight, however, was a powerful positive distal predictor of adolescent size. The daughters of heavier mothers produced less leptin per unit fat mass. Under conditions of high energy expenditure and low intake, adolescent women who were growing in height mobilized adipose stores and acquired lean mass, while developmentally older women maintained fat stores at the expense of lean mass. Married adolescents in the sample were older, had lower fasting C-peptide of insulin, had higher absolute energy expenditure, and spent more of their total energy budgets in activity than did unmarried peers.Human Evolutionary Biolog