I hadn't weighed myself in over 2 months. I've been eating at roughly maintenance through the holidays, but started a recent cut last week. I expected to weigh in within a range. I did, within a couple of pounds. That was yesterday.
This morning, I weighed in at 1.4 pounds less. Should I be thrilled about that? (I'm not).
Was it a whoosh? Maybe. Was it fat? Definitely not (I didn't eat -5900 calories yesterday); maybe a portion of it was. Was it the loss of water or a fluctuation? Probably.
I've been controlling caloric intake via a food scale for almost two years now. It always works.
If I took those two scale numbers in a vacuum, I could conclude that my deficit is working. But would I be correct? On the other hand, I know that the last 2 days, my deficit has been 870 and 1070 (approximately) - a little bigger deficit than I plan for.
The answer is that I trust the food scale far more than the bathroom scale. If I carry a 500 calorie deficit (or more) today, it's just as likely I'll have 2-3 pounds more (or less) on the scale tomorrow.
Just a real world example that you can't know in the short term. I preach on data windows being 6-8 weeks or more. If I was wanting to results every day, and didn't know what I know now, I would be thrilled about how my diet was "working" - not realizing that this fluctuation probably happens when I'm trying to gain or trying to maintain. Two data points. Not enough to base a conclusion on. If I would have weighed in at 1.4 pounds more instead of less, knowing that my deficits were what they were, could I conclude anything? (Don't answer; it's rhetorical - I have no basis yet for any type of conclusion).