My guess is it's that time of month (TOM). Did you know that we females gain on average anywhere from 4-8 pounds right before/during TOM and don't lose it until several days after our TOM completely ends? It's true! Doctors consider a gain of 8 pounds of water weight to be completely normal, and some women gain even more water weight than that (sometimes 10 pounds), especially if they give in to a craving for salt or something like that.
Most of us don't notice it quite as much until we start to diet. Since we are watching that scale like crazy when we are dieting, we REALLY notice that 4-8 pounds of water weight gain!
In fact there is no way your weight gain is anything BUT water weight since it went on so quickly.
So please, please don't give up. You have actually lost a ton of weight already, and although I think 12 lbs. is a little much to expect to lose each month, you could pretty easily lose 5 lbs. a month. Just imagine where you will be this summer if you lose 5 lbs a month! Think how much better your clothes will fit and how much more comfortable you will be!
It is a bit of a sacrifice to give up pizza, chocolate, french fries, etc., but isn't your health and happiness worth the sacrifice? At least on this way of dieting, you don't have to starve yourself and stay hungry all the time. I mean, any diet involves some sacrifice, but this diet to me is doable whereas starvation diets aren't so doable. Although, people are different, and maybe not everyone would like this WOE.
Please hang in there and post again in about two weeks. Bet you anything those pounds will be gone again and will take a pound or two with them when they go.
