Dr. Susan Brown of BetterBones.com recommends using a weighted vest to increase the effectiveness of walking as a weight-bearing exercise for building bone strength, especially for thin women of 114 pounds or less. My doctor recommended something similar: a bookback with a few heavy books inside. Nowadays, though, my I walk carrying one of my beautiful grandbabies, which is fun for both of us!
If you have a moment, take a look Dr. Brown’s informative article on the subject: http://www.betterbones.com/blog/post/Thin-women-and-hip-bone-loss.aspx.