Cars as a metaphor for understanding obesity

If we want to understand the accumulation of excess body fat, it's tempting to focus our attention on the location that defines the condition: adipose tissue.  Ultimately, the key question we want to answer is the following: why does fat enter adipose tissue faster than it exits?

It follows that if we want to understand why obesity occurs, we should seek to understand the dynamics of fat trafficking in adipose tissue, and the factors that influence it.  Right?

I don't think this is right, and here's a metaphor that explains why.

The speed of a car depends primarily on the force that its wheels exert on the asphalt below them.  If we want to understand why cars move quickly sometimes, and slowly at other times, we should seek to understand the dynamics of how force is transferred from the wheels to the asphalt, and the factors that influence it, right?

As you may have already surmised, that wouldn't be a very effective way of understanding car speed. To understand car speed, we have to move up the causal chain until we get to the system that actually regulates speed-- the person in the driver's seat.  Looking at the problem from the perspective of the wheels is not an effective way of understanding the person in the driver's seat.  Once we understand the driver, then we also understand why the wheels move how they do.

Similarly, in obesity, we have to move up the causal chain until we find the system that actually regulates body fatness.  The only known system in the human body that regulates body fatness is the brain.  Once we understand how the brain regulates body fatness, we'll understand why fat enters adipose tissue faster than it exits sometimes, eventually leading to obesity.

We already know a lot about how this process works, and that's why I focus my attention on the brain and behavior rather than the biochemical mechanics of adipose tissue.