Height of embedded video too small and not scaling

Hi, Please see http://theholyfish.com/chocolate-only-diet-day-5/ . The video window scales horizontally to the browser size, but the height stays fixed (and too small except on a very narrow screen). The code I used is: <p style="text-align: center;"><iframe src="https://www.youtube.com/embed/dB4kiR4--Uw" width="560" height="315" frameborder="0" allowfullscreen="allowfullscreen"></iframe></p> Thanks, Mat.