My SIL was telling me how her DD would sleep long during the day and in very short snippets at night, and because the DD had decided to stop nursing at 4 months SIL ended up having to give her formula, which further decreased the amount of sleep she got because she had to get up and prepare it. And apparently she couldn't nap during the day either! She survived though, and she said it was much easier with her next baby, who breastfed longer. So yeah, formula does not = more sleep!
As for the original question, I also don't pay attention to calories. I tend to ignore hunger out of laziness, so I often don't eat until I'm actually really hungry. But I don't notice a huge difference in appetite actually. I suspect I'm not eating "enough" calories overall, but I feel fine and the food I do eat is mostly quality.