If you're cutting carbs several days a week, you'll need to increase your protein and fats on those days to keep your calories from dropping too low. This is were shakes can come in…
Additionally, any time you make fat loss your goal, you risk losing plenty of fat burning muscle tissue along with the soft stuff. A healthy protein intake (do not replace your meals with your shakes) and supplemental BCAAs can both help you hold on to lean mass, while the BCAAs can also help with recovery between your workouts.
When someone wants to lose fat, particularly by an ambitious deadline for holidays, wedding’s, Christmas, birthday’s “I wanna lose a stone by next week” you name it I’ve heard it, the first supplement that usually comes to mind is a fat burner.
While this can definitely help and I’m not saying rule it out, it's a tool that should only be used when you have your nutrition and training on point.
Cover those crucial nutritional bases first, and you'll give your fat burner and your workouts a better chance of working for you.