Hi Thomas Howard. 500-600 calories per day seems very low. But to get some expert advice on why this may or may not be a good thing, I'm going to tag our nutrition expert, Chris Mohr. I suspect Chris will be able to offer some valuable insight.

This seems like a very unhealthy answer, because 5-600 calories is barely enough to keep your metabolism up and your brain functioning properly. It would be more effective to have 6 days eating healthy, one day eating whatever you want.