What Does MRI Report - Diffuse Hypo Intense Bone Marrow Signal Indicate

I am 41, 130lbs 5ft 4". I have a lower back injury and went for an MRI ,the results came back and had an additional info that I don't understand.It says: there is relatively diffuse hypointense bone marrow signal seen throughout the lumbosacral spine which diminishes the sensitivity of the examination in the detection of small focal osseous lesions and can be seen on a normal variation basis or in the setting of obesity,chronic smoking and/or a reactive shift to red hemopoietic marrow associated with systemic disease states,such as chronic anemia.a hemosiderosis might also produce the MRI signal