It may be personal information, but as I have experienced from speaking with others who have lost weight, many do like to share their motivational stories with other who were in the position they were once in. In addition, they are telling me their stories anonymously so I am not subjecting their privacy in anyway.
How exactly are you "protecting" the members? I don't believe they need your protection. If they don't want their story in my motivational book they don't have to respond, simple as that.
However I feel that if the people who have lost weight feel as good as I do about dropping the pounds, they would want others who were in their position to have the motivation and hope for change.
Why do I feel I can write a motivational book? Because when my daughter was born and I was to out of shape to even bend down and play with her, or even go to the park with her, I knew I needed to change. I received support from a dear friend who made my weight loss journey much easier and I want to offer the same support and hope I received to others who have been in mine, as well as many other's position.
Hearing stories of success as well as the reasons to change will show others weight loss is not impossible.