If you really over-eat on occasion, how long does it take for the extra weight to show up on your body and on the scale?

I can’t answer the first part of the question, but I can answer the second part. If you’re eating fattening foods, then not eating for an entire day, you’re going to gain more weight than you would if you ate something fattening, and then ate something else along with it.

When you stop eating, even if it’s only for a day, your body stores the food it does get, instead of burning off the excess like it normally would. So, when you eat something fattening, it’s going to be even more pronounced and your body will save it all for the energy needed to go about your day. In order for your metabolism to work, it has to have fuel (food). With no fuel, it saves the energy (fat) as a standby fuel source. You can see the kind of cycle this will lead up to.

Ok. Let me rephrase. If I eat 1500 calories, day in and day out, and I weigh 130 pounds and it doesn’t fluctuate, and suddenly, one day I eat 3500 calories, 2000 more than I usually eat, that will add up to roughly a ½ pound weight gain. The next day I go back to 1500 calories, but that ½ pound weight gain is still lurking…but as of when? Will I weigh 130.5 two hours after I ate the extra 2000, two days after? When? Eventually, since I drop back to the 1500 calories per day, day in and day out, that half pound will go away…but again, how soon? Pretty sure at the same rate, but I want to know what that rate is.

Pretty sure I just got the Perfecto-Fish award!

3 seconds! And 3 years to get rid of it!

Too many variables short term. Especially the hydration level of your body. I would wait 3 days at least.