DoseResponse Relationships Between Energy Availability and Bone Turnover in Young Exercising Women*
Rayan Ihle and Anne B Loucks
ABSTRACT: 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 doseresponse 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. Materials 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 random order. Blood was sampled at 10-minute intervals, and urine was collected for 24 h. Samples 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 (ZNTX-OC and ZNTX-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
What population led to the need for this article?
What is OC? What purpose does it serve? (This isn’t found in article. You need to research and cite your reference).
What is the caloric threshold for negative effects?
Opinion:
Osteoporosis is one of the risks with a low-calorie diet, explain another and how it can be fixed with proper nutrition.
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