Is Bone Marrow a Fat? The Truth Behind the Soft Tissue in Your Bones
                                
                                
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                                    4 min read                                
                            
                                Bone marrow accounts for approximately 4-5% of an adult's total body weight.  The definitive answer to the question, "is bone marrow a fat?" is that it is both a blood-producing tissue and a storage site for fat, existing in two distinct forms: red and yellow marrow.