Change in energy stores = Energy intake – Energy expenditure
According to my biochemistry professor in college, this had one - and only one - interpretation: The change in energy stores is controlled by energy intake and energy expenditure. The right side of the equation controls the left side of the equation. Also, there was an implied "just eat less and exercise more" (that energy intake and expenditure are independent variables).
But Taubes suggests that the causation could be reversed, and that energy intake and expenditure are dependent variables. In other words, a metabolic change could cause a change in energy stores, and energy intake and expenditure would change to match.
That (amazingly!) translates to: if you are losing weight you are likely to be less hungry and likely to have more energy. Or perhaps, if your metabolic state is such that you are losing weight, your hunger will adjust to match your activity level. Or even, if you're burning fat, you will only eat to make up for what you aren't getting from stored fuel.
It makes sense to think that if your energy stores are releasing fuel into the blood stream you would be less hungry (I'm assuming that hunger signals are a function of available fuel to some extent).
Naturally, we eat for nutrition as well as fuel, so I suppose it can't all be broken into thermodynamics, but it's an interesting way of thinking about it!