title: Effect of fasting versus feeding on the bone metabolic response to running.
abstract: Individuals often perform exercise in the fasted state, but the effects on bone metabolism are not currently known. We compared the effect of an overnight fast with feeding a mixed meal on the bone metabolic response to treadmill running. Ten, physically-active males aged 28 ± 4y (mean ±SD) completed two, counterbalanced, 8d trials. After 3d on a standardised diet, participants performed 60 min of treadmill running at 65% VO(2max) on Day 4 following an overnight fast (FAST) or a standardised breakfast (FED). Blood samples were collected at baseline, before and during exercise, for 3h after exercise, and on four consecutive follow-up days (FU1-FU4). Plasma/serum were analysed for the c-terminal telopeptide region of collagen type 1 (β-CTX), n-terminal propeptides of procollagen type 1 (P1NP), osteocalcin (OC), bone alkaline phosphatase (bone ALP), parathyroid hormone (PTH), albumin-adjusted calcium, phosphate, osteoprotegerin (OPG), cortisol, leptin and ghrelin. Only the β-CTX response was significantly affected by feeding. Pre-exercise concentrations decreased more in FED compared with FAST (47% vs 26%, P<0.001) but increased during exercise in both groups and were not significantly different from baseline at 1h post-exercise. At 3h post-exercise, concentrations were decreased (33%, P<0.001) from baseline in FAST and significantly lower (P<0.001) than in FED. P1NP and PTH increased, and OC decreased during exercise. Bone markers were not significantly different from baseline on FU1-FU4. Fasting had only a minor effect on the bone metabolic response to subsequent acute, endurance exercise, reducing the duration of the increase in β-CTX during early recovery, but having no effect on changes in bone formation markers. The reduced duration of the β-CTX response with fasting was not fully explained by changes in PTH, OPG, leptin or ghrelin.
authors.affiliation: Human Sciences, QinetiQ Ltd., Farnborough, UK. jscott1@qinetiq.com
authors.forename: Jonathan P R
authors.initials: JP
authors.lastname: Scott
authors.forename: Craig
authors.initials: C
authors.lastname: Sale
authors.forename: Julie P
authors.initials: JP
authors.lastname: Greeves
authors.forename: Anna
authors.initials: A
authors.lastname: Casey
authors.forename: John
authors.initials: J
authors.lastname: Dutton
authors.forename: William D
authors.initials: WD
authors.lastname: Fraser
mesh_terms: D000328:Adult; D001862:Bone Resorption / Q000097:blood; D001842:Bone and Bones / Q000378:metabolism*; D005215:Fasting / Q000097:blood / Q000502:physiology*; D054439:Ghrelin / Q000097:blood; D006801:Humans; D020738:Leptin / Q000097:blood; D008297:Male; D015675:Osteocalcin / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood / Q000378:metabolism; D011347:Procollagen / Q000097:blood; D012420:Running / Q000502:physiology*
chemical_list: D054439:Ghrelin; D020738:Leptin; D010281:Parathyroid Hormone; D011347:Procollagen; D015675:Osteocalcin