What is it about?

Typically exercise increases bone density. However in this experiment, mice that were calorically restricted failed to have an exercise-induced increase in bone, and even suffered harm to bone health. Bone fat (also known as marrow fat or marrow adipose tissue) is poorly understood. We confirm that bone fat increases significantly with caloric restriction. Interestingly a regulator of fatty acid uptake CD36 is significantly increased in , which may account for the rise in bone fat. Though the purpose of bone fat remains unclear, the fact that exercise reduces it as it does other fat depots (even in the setting of calorie deprivation) suggests it is an energy depot.

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Why is it important?

Exercise typically reduces bone marrow fat ( likely used as fuel for bone formation , based on prior work) . In caloric restriction, exercise lowered bone fat but this did not yield bone formation, suggesting an alternate function for bone marrow fat in this setting.


I care for patients with osteoporosis who are keenly interested in lifestyle measures to improve bone health. Many of my patients are post-menopausal women or older men that have low bone density and may have even had osteoporotic fractures. Based on this work, I advise that mild caloric restriction (particularly with a normal BMI) might prevent exercise from improving bone health, and in combination with exercise can even result in skeletal harm.

Dr Maya Styner
University of North Carolina at Chapel Hill, Department of Medicine, Division of Endocrinology

Read the Original

This page is a summary of: Exercise degrades Bone in Caloric Restriction, despite Suppression of Marrow Adipose Tissue (MAT), Journal of Bone and Mineral Research, September 2019, Wiley,
DOI: 10.1002/jbmr.3872.
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