I find if I force my calories down against hunger, I'll become sort of lethargic. But generally if I have some weight to lose and my appetite decreases after a diet change, I'll have more energy while eating less calories.

I've seen a number of plateau or even brief weight gain anecdotes from people who were water fasting. A pound or two of fat loss per week is a fairly respectable rate of loss, over the short term, fluctuations in body water can easily obscure what's happening with fat balance.