The most effective things I've found are: giving up drinking (not fun but it helps weight loss like you wouldn't believe), making sure you drink lots of water, writing down what you eat (it's easy to think you're 'watching' it but so much slips by unnoticed), checking whether you are losing inches rather than pounds (you could be firming up even if there's still some weight to go - especially if you are weight training) and making your runs harder, eg either faster or hillier courses. Hope this helps! I'm struggling after a race, then holiday, then bad cold, to get back into it - so you're not alone!