A Short-Term Ketogenic Diet Impairs Markers of Bone Health in Response to Exercise
Ida A. Heikura, Louise M. Burke, John A. Hawley, Megan L. Ross, Laura A. Garvican‐Lewis, Avish P. Sharma, Alannah K. A. McKay, Jill J. Leckey, Marijke Welvaert, Lauren McCall, Kathryn E. Ackerman
Abstract
Objectives: To investigate diet-exercise interactions related to bone markers in elite endurance athletes after a 3.5-week ketogenic low-carbohydrate, high-fat (LCHF) diet and subsequent restoration of carbohydrate (CHO) feeding. Methods: World-class race walkers (25 male, 5 female) completed 3.5-weeks of energy-matched (220 kJ·kg·d-1) high CHO (HCHO; 8.6 g·kg·d-1 CHO, 2.1 g·kg·d-1 protein, 1.2 g·kg·d-1 fat) or LCHF (0.5 g·kg·d-1 CHO, 2.1 g·kg·d-1 protein, 75-80% of energy from fat) diet followed by acute CHO restoration. Serum markers of bone breakdown (cross-linked C-terminal telopeptide of type I collagen, CTX), formation (procollagen 1 N-terminal propeptide , P1NP) and metabolism (osteocalcin, OC) were assessed at rest (fasting and 2 hr post meal) and after exercise (0 and 3 hr) at Baseline, after the 3.5-week intervention (Adaptation) and after acute CHO feeding (Restoration). Results: After Adaptation, LCHF increased fasting CTX concentrations above Baseline (p=0.007, Cohen’s d=0.69), while P1NP (p<0.001, d=0.99) and OC (p<0.001, d=1.39) levels decreased. Post-exercise, LCHF increased CTX concentrations above Baseline (p=0.001, d=1.67) and above HCHO (p<0.001, d=0.62), while P1NP (p<0.001, d=0.85) and OC concentrations decreased (p<0.001, d=0.99) during exercise. Exercise-related area under curve (AUC) for CTX was increased by LCHF after Adaptation (p=0.001, d=1.52), with decreases in P1NP (p<0.001, d=1.27) and OC (p<0.001, d=2.0). CHO restoration recovered post-exercise CTX and CTX exercise-related AUC, while concentrations and exercise-related AUC for P1NP and OC remained suppressed for LCHF (p=1.000 compared to Adaptation). Conclusion: Markers of bone modeling/remodeling were impaired after short-term LCHF diet, and only a marker of resorption recovered after acute CHO restoration. Long-term studies of the effects of LCHF on bone health are warranted.