I need an explanation from all you diet geeks :)

AGGUK73

Hi as the title suggests I want to understand the scientific reason for rapid weight gain. I will explain: I've been following MFP for 9weeks & have lost 9lbs on 1200 cals per day. I only have 4lbs to go, so only had a small amount of weight to lose. However I never strictly follow it on Sat/Sun as I prefer to have fun socialising. Some weekends I know I go way over, & others not so much, but it still seems to be working as I am very dedicated Mon-Fri. Yesterday (sun) we had a family day out, I didn't go mad but had a few beers, some chips by the seaside & an ice-cream cone. I NEVER weigh myself after a weekend, but as a one off I decided to see what I weighed this morning. I had gained 4lbs in 1 day!!!!! Now I obviously know this isn't pure fat, so my question is what is it & why/how can this happen in 1 day??
Now I'm confident that come next Sat morning when I weigh myself I will have (hopefully) dropped another 1lb. I'm going on hol in 3 weeks & we are staying all inclusive for a week. I refuse to be so obsessed with my weight that I wont have a good time on hol & eat/drink what I want, and it will be ALL the wrong things. I know I will come back quite a few pounds heavier & that's fine cos I will have had a great hol (I hope). But if I can try & understand this large weight gain in just a few days then it may help me shed them easier??
Please help :-) Many thanks.

LoraF83

It's probably just the excess sodium from the weekend causing water retention. It's not actual fat.

I'm up 3 pounds this morning. It will be gone (and then some, hopefully!) by Friday. No big deal!!

pattyproulx

Ya - it's water retention from an increase of sodium and carbs.

I'm low-carb and if I have a terrible weekend, I can literally gain 7-8 pounds. It's usually back off within a couple days though.