Jbug...all good advice here.
I have had the same problem for years, but recently I've been using Chia...yes...the same as chia seeds for the chia pet. You can buy it ground or whole seeds in packages at healthfood stores or online. I've bought it at Amazon.com as well as at Healthy Life Market at Drug Emporium. I first heard about chia when I read the excellent book, Born to Run (no, I'm not a runner, LOL). It's called the "Aztec super food."
Anyway, chia is a great source of fiber and antioxidants. Also good for apetite control as it tends to retain water in the tummy and swells a bit, thus reducing hunger. It's good for you, and I find it works far better than bran or even Metamucil! Look it up on the Internet, and you'll find much more about it.