[omginternets]

They haven't.

The body is not a closed system.

The laws of thermodynamics tell you your caloric equations have to be balanced, but the internal state of the body can alter behaviors such as feeding and moving, so appealing to the laws of thermodynamics is pretty much off-topic. It's a common fallacy, and you're not alone in committing it. Obesity is increasingly seen as a metabolic disease with behavioral consequences rather than the other way around.

Here are two arbitrary papers I've blindly pulled out of the google-scholar hat, both of which discuss aspects of the issue at hand. Much has been written on the subject, and I respectfully urge you to investigate further.

1. http://www.nature.com/nrendo/journal/v2/n8/abs/ncpendmet0220...

2. https://nutritionj.biomedcentral.com/articles/10.1186/1475-2...

Also, if you're going to be sardonic, you really should make sure you're not missing anything...