I'm certainly aware that many amputee support group leaders have physical limitations that I don't have, and that it may just not be possible for them to be as active as I am. But if you can walk, walking is better than sitting. If you use a wheelchair, rolling around is better than staying in one place. If you only have one arm, wave it occasionally. And we can all smile and speak enthusiastically with a big voice.
Eye contact is a critical form of body language.
If you also lean toward the speaker, that simply strengthens the favorable effect. I love it when the discussion gets active and energetic and when everyone is anxious to speak. It's my chance to play body language traffic cop. I point my finger to tell someone to speak. I hold my palm up to someone who's interrupting.