I suggest not looking at the scale. One bad day will cause your weight to go up because of water retention as well but if you get back on the rail, you will lose it again. Weight fluctuates all the time. It’s not linear.
Without any specifics, nobody can answer this question, not even approximately. If you weigh yourself tomorrow, you will probably see a significant increase, but most of it will be water weight. Continue your fasting routine as you began, and don’t worry too much about a few bad days.
This will not hinder your long term progress! Remember, success is the summation of consistency over time, not being perfect every single day. For me, I want to be healthy so that I can go and enjoy the moments that make life worth living—like birthdays, holidays, special occasions, etc.—without guilt, knowing I can and will just get back on track the next day.
Any change you see on the scale will likely be due to increased sodium / carb intake, stress, sleep, hormonal cycles and states, etc. You would have to eat an additional 3,500 calories on top of what your body actually uses in a day to gain even one pound, and even then, that will fall away quickly.
Don’t be so hard on yourself. What’s the point of finding health if it’s so restrictive you can’t even celebrate with your loved ones on special occasions? Just get back to it—you’ve got this! 💖
Have a cheat day every now and then. Think of it as a reward for the hard work. You may see a couple of lbs for a day or two but it will fall back off quickly. Sometimes a cheat day can also help break through a plateau.
You’re fine, one day is no big deal. Just go back to fasting and maybe in the future plan occasional cheat days.
If you continue to dwell on your perceived failure it will make it harder to continue your fasting path.
This guy did a 10k calorie challenge and tells you how much fat you end up gaining.
TLDR: like 1.6 pounds at most. You might weigh super heavy right after you ate all those food because you added alot of food mass in your body which retains water.