I know this is an older discussion but I'm in a similar situation and I'm wondering what you've learned and how this has played out for you over the last year?
I'm relieved to find a post related to hormone changes as the potential source of weight gain. I weaned about 3 months earlier than originally planed, quite abruptly. Let me back up, much to my surprise, I lost all of my pregnancy weight within a couple of months after giving birth, without exercising and while eating a heartily. I chalked it up to the baby being a hearty eater and it may also be hereditary as my sister did the same. However, she was in her mid-20's and I'm in my late 30's, so I was expecting to have to work for it. It's been 3 months since weaning and I have gained 10-14 lbs (depending on what time of day I weigh, which varies by 4 lbs in the same day, btw). Shortly after weaning I started exercising regularly again for the first time since birth, almost 2 yrs ago. Before, I could swing a random hike or yoga class but nothing regular. I've been a long-term healthy eater (gluten free for almost a decade now) and I've always been able to maintain my weight through walking. In the past, if I gained a couple of lbs and my clothes felt a little snug, I start walking, maybe two miles a couple times/wk and typically see results almost immediately. The last month I've increased my walking to 4 miles a day 4-5 days a week and have gained weight!?! I work at home and my job has been incredibly stressful all year, working wasn't planned but is a result of partner's job situation. When I started walking after weaning, it was really more to deal with the adrenaline/cortisol and stress from relentless deadlines, it felt necessary for my sanity. At the time my weight wasn't bothering me yet, I noticed a couple of lbs after a trip and thought, "added benefit, walking will knock that out." As fall dawns, I'm looking at needing a new wardrobe, going up a size for the first time in 2o+ years. It's challenging to accept. Additionally, I have been noticing that as soon as I ovulate I experience PMS symptoms -- irritability, impatience, cry easily, tender lower abdomen -- which just escalates over the next two weeks until I'm incredibly crampy and last cycle I had a migraine the day before. I'm also becoming less regular. So, obviously there's some hormonal imbalance, it's just somehow a relief to think the weight gain is related, too, and that I may be able to resolve both. I hope I don't have to choose between living at an uncomfortable weight and being obsessive to maintain a comfortable one. (What I mean by comfortable is that I find being at the mid to low range of my bmi recommended weight physically more comfortable. For example, my legs are so chunky that I can't sit comfortably on my knees lately.)