Can Botox reduce muscle mass in arms or legs?

This is the basis for using BOTOX to treat muscle spasm.  The down side is muscle weakness and reduced function.  So it would not make sense to use BOTOX say to reduce calf muscle size.  Most people what bulk in their limb muscles.

The amount of Botox to do that would be incredibly large and that can have serious, even life-threatening side effects.

Don't do it even if someone offers you to do it for you.