The Math is a Lie

Nope, but I'm pretty damned sure it's not 450, or 600 or even 800.  And, I'm also pretty damned sure she's right, that trying to lose weight by consuming only 450 calories a day is NOT a good idea.  You simply can't provide your body with the nutrition it needs, and maintain muscle at that level.  I don't believe there's a bariatric surgeon or nutritionist out there who'd advocate that as a strategy toward the end of someone's weight loss journey.  Because to suggest someone should drop to 450 to lose if they're not losing at 600 is to suggest they've reached caloric balance with their current weight at 600.