After Workout/Tropical Smoothie?

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I'm going to a spin class tonight which is going to burn a ton of calories for me, but I'm not going to be getting home until late, and I don't want to eat dinner before the gym, so I was thinking about just stopping by Tropical Smoothie and grabbing a smoothie and having that for dinner after. Does anyone recommend a certain smoothie from there that will help me out with weight loss and won't completely screw up the work I just did in the gym before hand? they have protein packed smoothies and such. Should I be looking for any particular ingredients in one if that's what I end up doing? HELP I'm sooo new to all of this! :(