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don't pig out, but don't reduce calories either. your days off are for recovery and the extra food will help your body to recover.
please take this advice and not the post above me, as your metabolism will be elevated and I assure you eating the same as your workout days (minus the shake) will not make you get fat..
also, working out 6 days a week is not a good thing, I will NEVER workout more than 4 days a week and normally no more than 3. There is such a thing as overtraining, but I hope you are eating enough to compensate for the abuse you put on yourself..