When you think about it, even the best-designed machines are not capable of holding a candle to the human body. Sure, we hurt easily. We die eventually. A disease can wreck havoc and leave us debilitated. Even the best-designed machines probably have a shelf life of two or three decades at best, if that. We are yet to design a device that can self-heal. We are probably still far away from machines that get better with us. Our incredible human body truly gets better with use. Your muscles get stronger with use. Your brain gets sharper when pitted against the best. Your bones get stronger when subjected to external force. Any half decent engineer would tell you, this is rare.
Traditionally, we have thought of fat as that which exists say in your belly. Research at the University of Michigan, my alma mater, has found fat in the marrow of the bones of rats. They have named it marrow adipose tissue or MAT. Humans, it appears to possess, similar fat. MAT seems to play a role in metabolism and also increases with the onset of Type I Diabetes, increase in the brittleness of bones caused by Osteoporosis. There are two forms of MAT, regulated and constitutive.
Traditionally, MAT has been thought of poorly as it was believed to cause reduced bone mass. Also, the fat stored in your bones has not been known to fuel your calorific requirement or daily energy needs. Here is where it gets interesting. Exercise seems to have a positive impact on bone marrow fat. In research conducted on mice, obese mice were found to have higher levels of the fat in their bones. When they exercised, they showed a marked reduction in their overall counts. Simultaneously, this also thickened and strengthened the bones.
There is a maxim that goes “What does not break you will make you stronger.” In the case of your bones, this is literally true.