Effect of alternate day fasting on markers of bone metabolism: An exploratory analysis of a 6-month randomized controlled trial

BACKGROUND Alternate day fasting (ADF) is a novel diet therapy that reduces body weight, but its effect on bone health remains unknown. OBJECTIVE This study examined the impact of ADF versus traditional daily calorie restriction (CR) on markers of bone metabolism in a 6-month randomized controlled trial. METHODS Overweight and obese subjects (n = 100) were randomized to 1 of 3 groups for 6 months: 1) ADF (25% energy intake fast day, alternated with 125% intake feast day; 2) CR (75% intake every day); or 3) control (usual intake every day). RESULTS Body weight decreased similarly (P < 0.001) by ADF (-7.8±1.2%) and CR (-8.8±1.5%), relative to controls by month 6. Lean mass, total body bone mineral content and total body bone mineral density remained unchanged in all groups. Circulating osteocalcin, bone alkaline phosphatase, and C-terminal telopeptide type I collagen (CTX) did not change in any group. IGF-1 increased (P < 0.01) in the CR group, with no change in the ADF or control group. When the data were sub-analyzed according to menopausal status, there were no differences between premenopausal or postmenopausal women for any marker of bone metabolism. CONCLUSION These findings suggest that 6 months of ADF does not have any deleterious impact on markers of bone metabolism in obese adults with moderate weight loss.