Try to calculate the calories for the meal, eat extra lightly the other meals on the same day and for the next day. Don't make this a habit, maybe once a week or every two weeks only. For me, short answer to this question is, yes, it does affect you. However, you can still be smart about it and eat extra healthily on the same day, day before, and day after.

I haven't had any real cheats. My plan is simply to stay within my calorie range +or - about 100 pounds. Last night I went out for planned Mexican and made good choices knowing ahead of time the calorie amount. We were with friends and everyone wanted to go to DQ. I didn't know the amounts but assumed a dipped ice cream cone would be similar to McDonald's and I still had 200 calories left. Uh no...twice as much. (Also not as good. LOL!)

And I had no jump on the scale this morning.

One meal messes me up because I genuinely prefer junk food to "real" food and that one meal makes me start to crave more BADLY. I'm also really quick to binge so I just try to avoid it all!

Usually when I cheat, it's pizza. I make a diet version of pizza at home, but it's just not the same, kwim? So I do go out for pizza, probably about twice a month. And I don't worry about it. I usually still end up losing, or maintaining at the very least, because my diet is on track both before and after the splurge. This "might" be slowing my weight loss a little, but I'm okay with that, because it keeps me from going crazy. I think it actually helps to keep me on plan.

Like someone else mentioned earlier, I too, weigh once a week. If my weigh in is good, then maybe I'll have a splurge. If it's a bad weigh in, then I don't. I'm trying to make this a plan that's reasonable, and that I can live with long term. This is working for me. I also use the splurges to work in special events/holidays during the year. Like on Valentine's Day, I will likely go out for dinner and order what I want, but you can bet that my eating will be good both before and after that meal.

I let myself splurge a little everyday, but I'm pretty strict about it... I eat sweets/cookies because I eat between 1300 - 1400 cals and I exercise about 500 cals. I can maintain this because I let myself have a cookie or ice cream (it's usually FF, sugar free anyways) and I don't feel like I'm depriving myself. And I've been losing each week. I hardly ever go out because I've worked in so many restaurants, I know what goes into food. I'm usually disappointed in the food, too, because I've found so many tasty ways to make healthy food at home. Going out is just too expensive, too many calories, too disappointing... I can't really enjoy it.

I don't think one cheat is going to harm anything in the long run, aside from like you said the sodium content and water weight. But keeping it to just one cheat might be harder for some people than others, in terms of willpower.

I went out Friday night with a bunch of friends and had a few drinks, the low calories means the alcohol hits a bit harder, even with only a small amount.

Then I went home and ordered a steak and cheese sandwich (my particular downfall) and even though it was a small, I did eat the whole thing.

The only difference I noticed scale wise was that the next day was my WI (doh!) and my weight was the same as the WI last week, so obviously still retaining water from all the salt from sub.

A few days later though and my weight has normalized, no actual gain. So I learned from this 2 things: Don't drink and order takeout, and it sucks to feel salt-bloated, and no matter how good the food was it isn't worth it!