I have a stubborn belly too...for me it helps when I work out my back as well as my abs for a thorough core toning. In order to do this without gaining big muscles I use a weight vest when I walk and doing planks really helps. For me its about strengthening my entire core and not just focusing on my belly. Good luck! I did all of this while I was in the army and had to stay a certain weight I am 4 weeks out now and will try to keep updated as to what works for me...I am currently losing everywhere but my belly. I have hope it will eventually catch up as long as I stick to my plan