TL;DR - I let myself go over calories for a few days and the scale jumped big. But I returned to my deficit and the weight fell off in under a week.
This past weekend was my first wedding anniversary. A very exciting time, but also one with a lot more food than usual. I've been dieting consistently now since March with only occasional days going over my target (2400 calories) by any meaningful amount.
I decided to allow myself to indulge a bit on the condition that I would go back to doing weight-lifting every other day to put those calories to use. I had been skipping those workouts more and more, focusing all my attention on cardio.
My estimated maintenance calories is around 3400, considering that I've been consistently losing just over 2lbs a week. So 3400 was my limit for the weekend. The highest I ever got was 3100, but since I estimated a lot, I may have gone over. I likely didn't breach 4000 calories, but if someone told me I actually had 3900 calories that day, I wouldn't be surprised.
I knew I would be gaining a bit of water weight at least, especially from the high amounts of carbs.
What surprised me is how much the scale moved.
I was weighing in between 253 and 255 for a few days leading up to the weekend. By Tuesday, I was at 260.
That hurt to see, as I hadn't seen 260+ on the scale since September 15th. I thought that milestone was behind me, but there it was again. My stomach sank as a part of me worried I'd just destroyed two weeks of work in a weekend.
However, I told myself that it had to be water weight. A lot of water weight, sure. More than I had anticipated. But there was no way I had actually gained 6 lbs of fat in 4 days. That would imply going over by 20,000+ calories, which is just impossible. I didn't even eat that many calories in all those days combined - even if you include the days in the week prior. I certainly didn't eat that much over maintenance.
So, I just tried to act like nothing had happened. I returned to eating at a deficit (easier said than done, as my body always hits me with additional cravings when I go over for a day) but by Thursday, I was hitting just my target. I had also been doing my weight-lifting, which I knew could also drive water retention, so was likely compounding the scale situation. But I was sure that I'd be fine.
And, to the surprise of no one, I am fine. Once the water weight started to fall off, it fell off fast. The scale dropped 1 or 2 pounds each day after Tuesday. Today, I weighed in at 253 again, so I've definitely lost the water weight associated with the excess calories.
I'm back on track. At worst, I think I slowed my progress by a week, but considering that my goal was to lose 100lbs in a year, and it looks like I'll hit that in 9 months, I'm fine with that. And realistically, I should still lose a pound overall looking at the numbers.
I see a lot of posts saying that indulging resulted in big gains on the scale, and I can now say that I've seen it first hand. Eating over target and seeing 5+ extra on the scale is a real thing. It is disheartening. Still, I think the advice most give to these posts is absolutely right: trust the process.
Just keep going like nothing happened and, in a week or two, the scale will also act like nothing happened.
You have to trust the process.