Supplementary Energy Increases Bone Formation during Arduous Military Training.

PURPOSE To investigate the effect of supplementary energy on bone formation and resorption during arduous military training in energy deficit. METHODS Thirty male soldiers completed an 8-week military combat course (mean ± SD, age 25 ± 3 years, height 1.78 ± 0.05 m, body mass 80.9 ± 7.7 kg). Participants received either the habitual diet (control group, n = 15) or an additional 5.1 MJ·d to eliminate the energy deficit (supplemented group, n = 15). Circulating markers of bone formation and resorption, and reproductive, thyroid, and metabolic status, were measured at baseline, and week 6 and 8 of training. RESULTS Bone ALP decreased in controls (-4.4 ± 1.9 μg·L) and increased in the supplemented group (16.0 ± 6.6 μg·L), between baseline and week 8 (P < 0.001). P1NP increased between baseline and week 6 for both groups (5.6 ± 8.1 μg·L, P = 0.005). βCTX decreased between baseline and week 8 for both groups (-0.16 ± 0.20 μg·L, P < 0.001). Prolactin increased from baseline to week 8 for the supplemented group (148 ± 151 IU·L, P = 0.041). The increase in adiponectin from baseline to week 8 was higher in controls (4.3 ± 1.8 mg·L, P < 0.001) than the supplemented group (1.4 ± 1.0 mg·L, P < 0.001). IGF binding protein-3 was lower at week 8 than baseline for controls (-461 ± 395 ng·mL, P < 0.001). CONCLUSION The increase in bone ALP, a marker of bone formation, with supplementation supports a role of energy in osteoblastic activity; the implications for skeletal adaptation and stress fracture risk is unclear. The mechanism is likely through protecting markers of metabolic, but not reproductive or thyroid, function.