Winter Weight?

For someone who's always been struggling with her weight, hovering somewhere between 49 - 50kgs and trying hard to put on a few more, it came as a pleasant surprise when I realised I'd piled on 4 kilos in the 3 months that I'd been in Shanghai. Last night, approx. 4.5 months after my move, I found out that I've now hit a record high of 57kgs. While absolutely thrilled, I'm now starting to have a niggling fear of how fast I'd managed to gain all that. I mean 7 kgs in 4.5 months is pretty quick. And I'm not doing any more sports. I'm kinda hoping that this is all winter weight and I'll more or less stabilise once summer arrives. I doubt it though :s