For nutrition purposes, yes. For weight loss purposes, no.

Who told you this?  If it's your doctor, fire him.  This
is the sort of thinking that will get you malnourished.

If you eat less calories than you burn, you will lose weight, regardless of
where they come from.

Of course. Studies are quite clear that at identical calorie intakes,
different macro nutrients have different effects. See my article on that
issue:  http://www.brinkzone.com/nutrition-theory.html

It matters.  Your calorie load has to do many things:

1.) provide nutrients that power your body
2.) provide a feeling of satietion so you're not feeling hungry
3.) provide fiber
4.) other stuff I'm not thinking about but no doubt exists

So if you're going to try to get by on fewer calories then you are going
to have to pick those calories pretty carefully to meet your satietion and
nutrient and fiber requirements.  Each calorie should be selected with
some attribute in mind.  There just isn't anyone out there who thinks a
diet of 1000 calories a day is as sustainable as a diet of 1000 calories a
day where the 1000 calories are fairly balanced between fat (for EFAs and
satietion) and carbs and protein (for nutrients and satietion and fiber).

It takes some experimenting to figure out how to feed your body on a
calorie budget successfully over the long haul.  Try charting things at
www.fitday.com and keeping a food diary about how you feel after different
meals.  It will become clear if you pay attention.

I've been wondering for some time now how come my parents never taught me
how to feed my body.  OTOH, all I have to do is look at my two obese
parents to realize that they just didn't know themselves!  I have no idea
why the basic maintenance of a human body isn't common knowledge, but for
some reason it just isn't!

-- Wendy