I wouldn't delay TTC. I'd do exactly what you were considering.... try really hard between now and X'mas to lose as much weight as you can. If you went really hard core with diet and exercise you could lose quite a bit. Then when you're pg be really good with your food and hopefully you wouldn't gain as much. DH and I are going to start TTC #2 this month and I'm already planning to not put on as much weight this next pg. I put on I think about 18kg with DS (I only got to 35w1d). I lost 12kg straight away (within a few weeks) and then had to lose the remaining 6 after I stopped BF (nothing I did would shift it while my hormones were in BF mode). I got back into running after I stopped BF and have now lost 10kg in the last 4months. I REALLY don't want to put on 18kg again so I'm going to be watching my food while pg next time and restricting the chocolate and cheese