[sa1]

There are issues with the imbalance explanation. w.r.t obesity, the least wrong (and most explanatory) equation will relate calories going into adipose tissue, and calories being taken out of adipose tissue.

Then another less wrong equation can relate calories absorbed by the digestive system and the calories burnt by the whole body.

These are not the same equations as calories eaten vs calories burnt. And the quantities are not easily measured.

Depending on exercise, and other potentially unknown environmental or genetic or other conditions, the body will put energy into tissue other than adipose tissue.

Not all energy eaten will be absorbed. There was a recent study which showed how eating fructose expands the gut lining to be able to absorb much more nutrition. We do not know all the regulatory mechanisms that control absorption. Nor all mechanisms that control hunger.

We're far from understanding all aspects of nutrition. The imbalance equations needs to be refined, if people are looking up to laws of physics to explain this matter.