Yes, it means avoiding carbs/creatine due to the water retention but that's below the skin and not usually picked up by calipers.
If I'm wrong on that or you get more information please do tell.
The thing about calipers is that a single-site measurement isn't as accurate for women, because of our fat distribution, not to mention you need to have someone who's really good at using them to take your measurements consistently.
Even scales have to be used consistently, such as first thing in the morning. Single-point measuring, usually over the hip, is remarkably accurate for both sexes but why restrict yourself to single point? Some methods use 7 points, including over the shoulder blade which is tricky by yourself but there are other multi-point methods that can be done alone. If anything doing it yourself can be more consistent, as you tend to do the same thing every time. Getting someone else to do it may be more accurate technically but the whole point is simply to monitor trends and changes over time. That doesn't require much precision.
Nor do you really need a helping hand with a tape measure.
As for the mirror, yes, valuable things, especially for spinach in your teeth. However for a monitoring system they suck, badly. How you look will depend very much on how you feel at the time. If you just skipped a workout and feel lethargic I guarantee you that you'll look like crap in the mirror. If you know you've been working out hard lately and you just broke your bench record, you'll look so good it's freaky.
That's why, especially in this age of cheap digital photography, I urge peope to take pics. Comparing one pic to another taken in the same manner is proof positive, regardless of your mood at the time. A snappy boss and a long commute can put 10lbs on - in the mirror but not the camera. Cameras don't care what mood you're in, they just record what's there.
Likewise scales don't care about your bench record, your stronger bones, better endurance, slimmer waist and firmer arms, they just record gross weight.
OK, let me give an example. Recently I did the anabolic burst, it's where you basically starve yourself silly for a couple of weeks then stuff yourself stupid for a couple of weeks. The ratio between muscle lost and gained compared to fat lost and gained, mostly due to the crazy hormone swings you create, means in theory you gain muscle and lose fat, as an overall balance at the end. That's the plan.
Monitoring closely, with scales, calipers and tape. I was able to easily spot the point when it was no longer just fat weight coming off, at which point I piled on the food and was able to again spot when it was not just lean tissue being added. The system worked for me, not 14 days by 14 days, more like 9 days by 10 for me personally. Had I relied on nothing but scales when do I quit cutting? I was losing weight all the time, how far should I have gone?
BECAUSE I was using calipers and a tape as well I could spot the switchover, when my body went beyond using fat reserves - a scale could not tell me that.
Same with bulking.
Sure, if you're a fat blimp and just want to shed pounds, a scale will work. No need for anything fancy when you're that fat, just cut down on calories and you can't help but lose weight. So if we're just talking slimming, fine, diet and scales.
If you're talking balancing fat loss with muscle growth, that takes a little more care and balancing, but again not so much at high fat levels. The body is not good at using stored fat for muscle growth but you don't need to keep the calories so high either.
OK let's compromise - if you're a fat blimp and want to shed weight, diet and scales will do. If you're already fairly lean and wish to get ripped and muscular, scales and diet, even with working out, is too blunt a method. You might still get there but can easily head in the wrong direction or just quit making gains. Certainly you'll have to choose between bulking or cutting, I don't see how you could walk the tight-rope of holding onto gains while shedding fat if your only guide is a bathroom scale.
For a lot of people just cutting calories and getting slim is all they desire - or need.
Throw in some weight training and its even better, sure.
But if that's all you've got in your entire arsenal of tricks and techniques, it aint gonna get you much beyond 'slim'. If you're lucky and that's all your genetics required. We don't hear so much from those that failed.
I've far too many people who've struggled with weight, mostly guys it's true, that have spent a fortune on cutting supplements, worked out 5 or 6 days a week. "How much cardio do you do?" "Er.."
On the treadmill or elliptical a couple of times a week and hey, a 6 pack!
Who'd have thunk?
If anything women do too much cardio and should do more weights, true. Men are the opposite, they do more weights and little cardio. Both sexes benefit from doing a bit of the other.
But no, I don't accept the idea that 'cardio doesn't work' (or doesn't burn calories!). It DOES work, IF you mix it up a bit and don't do the same damn thing all the time. However the exact same thing applies to weightlifting, do the same thing all the time and that stops working too.
B.
Lots of people--we're called "Lurkers". I am a member of many fitness boards where I just read or occasionally lurk, and an active member of a handful where I spend most of my posting dollars. I joined this particular board long ago, but the atmosphere hadn't been one I felt much like contributing to. Until now. 
