A while back Demigan had a running series of posts about various aspects biological enhancement for the purpose of designing super-soldiers with an element of (pseudo) science behind them.
You can find his previous questions here:
One thing I didn't really see mentioned, which I was wondering about, is metabolism. Obviously, a super-solider with powered-up muscles, nervous system, etc. is going to be burning a LOT of energy, even at rest. The post about temperature control is basically asking how to deal with all the excess heat that is created as a result.
Metabolism is the process by which the body converts food/fuel into the energy it needs to function. The higher the energy needs of the organism, the greater the amount of fuel required, or the more efficient the conversion process must be.
In nature, we do see that some creatures have more efficient metabolisms than others. For instance, warm-blooded beasties have more efficiently designed metabolisms than cold-blooded beasties because they need to use additional energy warming their bodies and therefore need to use the energy that they have in a more efficient way.
Increasing metabolic efficiency would also probably help with the temperature problem a bit as well. This article notes:
no energy transfer can be perfectly efficient – that's a basic law of physics. Instead, each time energy changes forms, some amount of it is converted into a non-usable form. In the reactions of an animal's metabolism, much of the energy stored in fuel molecules is released as heat.
Logically, the more efficient we can make this conversion, the less heat will be produced as waste.
Given a super-soldier's high rate of energy usage, how do we stop them from needing to eat constantly, 24/7? The less we have to feed them, and the longer they can survive cut off from supplies, the better. Any ideas for improving these guys' metabolic efficiency or generally finding ways to feed them a more "normal" amount while still powering their high energy needs?
To stay in keeping with Demigan's posts, a good answer needs to be limited to a biological solution, where a body can build, repair and maintain it.