You can state your claim with certainty for those you've observed to be talking 500 cal but actually eating a lot more. But that's the limit.

Not tremendously sure what this means, sheila......but do you really believe that there are folk around who can be genuinely consuming a consistent intake of 500 Cals a day and not losing weight?

I'm not talking here about individuals who have some serious metabolic pathology going on........they'd be much better off to consult with a bone fide endocrinologist rather than a purveyor of crack-pot diet schemes.....but do you really have any reason to believe that a gen-U-ine and consistent diet of 500 Cals a day doesn't produce *weight loss* of some sort.

500 Cals a day. That's less than it takes to keep the Big Four organs going (a.k.a. heart, brain, liver, kidneys......called the Big Four because of their metabolic demand in relation to their respective sizes and importance to, well....life, I guess)

Without the Big Four getting their energy requirements from somewhere, you'd ultimately be looking at a 0 Cals a day requirement....as in a corpse!!