While I prefer doing Core, a couple of times this summer I've chosen to do Flex for a week. Each of those times I gained weight (less than 1/2 lb. usually, but a gain is a gain!), even though I was following Flex to the letter, using the same amount of WPA and exercising. When I'd switch back to Core, then I'd lose what I'd gain and more than I usually lose in a week.

I'm curious if anyone else has experienced this? If so, why do you think it happens? Thanks!

I have no clue whatsoever. There are also people who do Core to the letter but don't lose, so it's not the program choice I don't think. Maybe what you're eating to make up your points allowance isn't always healthy? Are there more snacks? Just trying to throw a few things out ... but really it doesn't make much sense, does it?

Usually the people following core to the letter and not losing are eating too big of portions or too many of the higher calorie choices and not enough veggies. How do you know you wouldn't have gained that week if you had stuck with Core...our bodies retain water, etc. so 1/2 a pound could be that.