Here's the post I was talking about:
Let's keep this simple.
Why doesn't our body utilize our existing fat stores as energy, to aid in hypertrophy (muscle building)?
You have to remember this very simple fact. Having an abundance of food at arm's length is a rather new dilemna, in the grand scheme of things. I mean, go back a thousand years and you were not able to eat, how we eat today. And 1000 years isn't that long even. Go back 10,000 years and wow, things were much, much different.
We did not have a continuous food supply. Excess food was not an issue and humans had to develop the ability to survive periods with low to no energy.
Because of this, our bodies want to store excess energy as fat. It is calorically dense and easily stored. On the flip-side, muscle is energetically costly. This means adding new muscle is not a *cheap* process in terms of energy (calorie) utilization.
Add to this, ultimately, aside from the base level of muscle that each of us has, additional muscle is worthless in our *body's mind.*
When the early man found a huge stash of food, he would gorge until he was full and then some. It doesn't take science to tell us that this will result in a gain of fat. He did this so that when the winter came and everything died or ran for the equator, he had enough energy to maintain life during this period.
Mind you, this went on for more years than you can fathom from your short time here on lovely Earth. Adaptation is an amazing thing. It takes a VERY long time to happen. Extremely slow process.
We adapted for survival during a time when food (energy) was scarce.
Back when, if the body decided to use a ton of energy to make muscle instead of fat, you would have stored less gross energy in a tissue that is harder to extract energy from, and ultimately it would have died during food-scarce periods.
To add to this, this is why we have many systems in place physiologically that ensure we don't under-eat. Stop eating for a few days. See how hungry you become. See how your cravings shoot through the roof. The endocrine system, primarily, is amazingly responsive to under-consumption of food.
Flip this. With over-consumption (something that is commonplace this day in age), not so much. Our bodies are relatively weak at detecting over-consumption due to the times long ago.
So, in a nutshell: Our bodies like storing fat for survival even though we don't need it today. Our bodies don't like storing muscle.
Hence, you're not going to find the conversion of fat into muscle as a common physiological act. At least not in the 21st century. Things might be different in the 31st.
