How can diseases cause obesity?

Question

I just watched an episode of House and he diagnosed a girl with Cushing’s – an illness that can cause obesity.

How is that possible? I was under the impression that our bodies use energy we get from food, and if it doesn’t get the food it’ll burn fat resulting in us getting slimmer – how can a disease change that?

How does it not go against some laws of thermodynamics? Maybe I’m just being silly.

In: Biology

Answer 1

> I was under the impression that our bodies use energy we get from food, and if it doesn’t get the food it’ll burn fat resulting in us getting slimmer – how can a disease change that?

It doesn’t change that. But it changes the details.

A given amount of food has a fixed amount of chemical energy. But our body doesn’t extract 100% of that energy! Different bodies extract it at different rates.

Similarly, the same activities/lifestyle will cost different people different amounts of chemical energy.

So, a person eating the same amount and doing the same amount of exercise might end up with different actual energy dynamics.

That’s what the metabolism is (simplified, of course).