The adolescent transition under energetic stress: Body composition tradeoffs among adolescent women in The Gambia.
OBJECTIVE
Life history theory predicts a shift in energy allocation from growth to reproductive function as a consequence of puberty. During adolescence, linear growth tapers off and, in females, ovarian steroid production increases. In this model, acquisition of lean mass is associated with growth while investment in adiposity is associated with reproduction. This study examines the chronological and developmental predictors of energy allocation patterns among adolescent women under conditions of energy constraint.


METHODS
Fifty post-menarcheal adolescent women between 14 and 20 years old were sampled for weight and body composition at the beginning and end of 1 month in an energy-adequate season and 1 month in the subsequent energy-constrained season in a rural province of The Gambia.


RESULTS
Chronologically and developmentally younger adolescent girls gain weight in the form of lean mass in both energy-adequate and energy-constrained seasons, whereas older adolescents lose lean mass under conditions of energetic stress (generalized estimating equation (GEE) Wald chi-square comparing youngest tertile with older two tertiles 9.750, P = 0.002; GEE Wald chi-square comparing fast- with slow-growing individuals for growth rate 19.806, P < 0.001). When energy is limited, younger adolescents lose and older adolescents maintain fat (GEE Wald chi-square for interaction of age and season 6.568, P = 0.010; GEE Wald chi-square comparing fast- with slow-growing individuals for interaction of growth rate and season 7.807, P = 0.005).


CONCLUSIONS
When energy is constrained, the physiology of younger adolescents invests in growth while that of older adolescent females privileges reproductively valuable adipose tissue.
Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA; MRC Keneba, MRC Unit, The Gambia; MRC International Nutrition Group, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK; and MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, CB1 9NL, UK.
Meredith W
MW
Reiches
Sophie E
SE
Moore
Andrew M
AM
Prentice
Ann
A
Prentice
Yankuba
Y
Sawo
Peter T
PT
Ellison
body composition; life history theory; puberty; reproductive ecology