No one thing (unless you have medical issues) is going to 'prevent weight loss'. At the heart of it all is calories in versus calories out.
I find that the detour bars aren't the best for me because even their low sugar ones are still pretty high in calories (at least for the large ones I have seen, though they may make a smaller one that I'm not aware of) so when I do eat protein bars I opt for the Quest bars.
Definitely check them out! They have them at GNC and they sell them online, but you really can't beat their nutrition stats. Not only that, but most of them are made with natural ingredients and none of them have that fake chocolate coating so they travel extremely well and don't melt!
http://www.questproteinbar.com/
My second favorite are the small sized Supreme Protein bars. They're a bit more candy bar-esque and don't travel as well but they also have some pretty respectible stats and feel like a treat.
http://www.supremeprotein.com/