It sounds like you don't have that setting option checked. You would need to go to your Friend Feed settings and check the box for you to share Weight Lost (when you weigh-in) and save your settings. Once you do that, your future weigh-ins will communicate with that feed and post that as you lose weight.
"Obstacles don't have to stop you. If you run into a wall, don't turn around and give up. Figure out how to climb it, go through it, or work around it." - Michael Jordan
Searching for a buddy? Try using the search feature in the SparkPages section.