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Effects of Energy Restriction and Exercise on Bone Mineral Density during Lactation

COLLERAN, HEATHER L.1; WIDEMAN, LAURIE2; LOVELADY, CHERYL A.1

Medicine & Science in Sports & Exercise: August 2012 - Volume 44 - Issue 8 - p 1570–1579
doi: 10.1249/MSS.0b013e318251d43e
Applied Sciences

Modest energy restriction combined with resistance training (RT) has been shown in nonlactating women to protect bone during periods of weight loss. However, there is a paucity of research on dietary interventions and exercise in lactating women aimed at promoting bone health and weight loss.

Purpose This study aimed to investigate the effects of energy restriction and exercise on bone mineral density (BMD) and hormones during lactation.

Methods At 4 wk postpartum, participants were randomized to either a 16-wk intervention (diet restricted by 500 kcal and RT 3 d·wk−1) group (IG = 14) or minimal care group (CG = 13). Measurements included BMD by DXA, three 24-h dietary recalls, and hormones. Repeated-measures ANOVA was used to test for group differences over time.

Results Energy intake decreased more in IG (613 ± 521 kcal) than CG (171 ± 435 kcal) (P = 0.03). IG lost more weight (5.8 ± 3.5 kg vs CG = 1.6 ± 5.4 kg, P = 0.02). BMD decreased over time, P < 0.01, with no group differences in lumbar spine (IG = 3.4% ± 2.5%, CG = 3.7% ± 3.3%) or hip (IG and CG = 3.1 ± 1.8%). Prolactin and estradiol decreased over time in both groups, P < 0.01. Basal growth hormone remained stable; however, there was a significant increase in growth hormone response to exercise in IG.

Conclusions These results suggest that moderate energy restriction combined with RT promotes weight loss with no adverse effects on BMD during lactation.

1Department of Nutrition, University of North Carolina at Greensboro, Greensboro, NC; and 2Department of Kinesiology, University of North Carolina at Greensboro, Greensboro, NC

Address for correspondence: Cheryl A. Lovelady, Ph.D., Department of Nutrition, P.O. Box 26170, University of North Carolina at Greensboro, Greensboro, NC 27402-6170; E-mail: Cheryl_Lovelady@uncg.edu.

Submitted for publication July 2011.

Accepted for publication February 2012.

©2012The American College of Sports Medicine