You can still loose weight and have those as a daily meal, but its not the best course of action. As long as your macros by the end of the day are in the vicinity of where they need to be for you to loose weight, i.e. below maintenance caloric intake, you will loose weight.
As far as where to use them in your diet. Personally I would use them as an immediate (10-25 minutes) before workout meal. I typically go about an hour to 1.5 hours before my workouts, but with the carb source being largely sugar, it will be more beneficial to take it closer to your workout to avoid any hypo issues.
Aside from the above and post workout I would say try to avoid the bars.