Not all the studies that investigated all the conditions in the triad , but the authors concluded that it seemed that athletes were in more severe stage of this disorder .
Dose-response relationships between energy availability and bone turnover in young exercising women.
UNLABELLED To help refine nutritional guidelines for military servicewomen , we assessed bone turnover after manipulating the energy availability of 29 young women . Bone formation was impaired by less severe restrictions than that which increased bone resorption . Military servicewomen and others may need to improve their nutrition to avoid these effects . INTRODUCTION We determined the dose-response relationship between energy availability ( defined as dietary energy intake minus exercise energy expenditure ) and selected markers of bone turnover in 29 regularly menstruating , habitually sedentary , young women of normal body composition . MATERIAL S AND METHODS For 5 days in the early follicular phase of two menstrual cycles separated by at least 2 months , subjects expended 15 kcal/kgLBM/day in supervised exercise at 70 % of aerobic capacity and consumed controlled amounts of a clinical dietary product in balanced ( 45 kcal/kgLBM/day ) and one of three restricted ( either 10 , 20 , or 30 kcal/kgLBM/day ) energy availability treatments in r and om order . Blood was sample d at 10-minute intervals , and urine was collected for 24 h. Sample s were assayed for plasma osteocalcin ( OC ) , serum type I procollagen carboxy-terminal propeptide ( PICP ) , and urinary N-telopeptide ( NTX ) . RESULTS NTX concentrations ( p < 0.01 ) and indices of bone resorption/formation uncoupling ( Z(NTX-OC ) and Z(NTX-PICP ) ; both p < 10(-4 ) ) were increased by the 10 kcal/kgLBM/day treatment . OC and PICP concentrations were suppressed by all restricted energy availability treatments ( all p < 0.05 ) . PICP declined linearly ( p < 10(-6 ) ) with energy availability , whereas most of the suppression of OC occurred abruptly between 20 and 30 kcal/kgLBM/day ( p < 0.05 ) . CONCLUSIONS These dose-response relationships closely resembled those of particular reproductive and metabolic hormones found in the same experiment and reported previously : similar relationships were observed for NTX and estradiol ; for PICP and insulin ; and for OC , triiodothyronine ( T3 ) , and insulin-like growth factor (IGF)-I. The uncoupling of bone resorption and formation by severely restricted energy availability , if left to continue , may lead to irreversible reductions in BMD , and the suppression of bone formation by less severe restrictions may prevent young women from achieving their genetic potential for peak bone mass . More prolonged experiments are needed to determine the dose-response relationships between chronic restrictions of energy availability and bone turnover
Not all the studies that investigated all the conditions in the triad , but the authors concluded that it seemed that athletes were in more severe stage of this disorder .