Hi Paul and Kitty
I hope you are well
Here is a report of a recent exchange between Olafur, you (Paul) and
me about the right use of rate in vernacular englsih

Here is the caption (I'm not sure about the term) of this dialog
>>>>>> Me (to Olafur)
>>>>> Olafur (to me)
>>>> Me (to Olafur)
>>> Me (to Paul)
>> Paul (to me)
>Olafur (to Paul)

I also wrote the initial of the author at the beginning of the line
in order to be clearer

[Thanks for doing that. With a three way inline discussion the "level
indicators" are not as easy to follow as with a dialog. --Paul]

[As an explanation, this email correspondence occurred on the side from a thread
discussion on calorie restriction between Olafur and Francois at
sci.life-extension a few days ago - http://tinyurl.com/5zao3x **Kitty]


F>>> Olafur and I are arguing about the right use of rate. Would
F>>> it bother you to enlighten us ? (I pasted below the recent
F>>> exchange with Olafur)

F>>>>>> Hi Olafur,
F>>>>>>
F>>>>>> I'm making my answer to your questions about my fat rate
F>>>>>> (which is much higher than you, you'll see)

O>>>>> Actually it's fat percentage not fat rate. As far as I know
O>>>>> the word "rate" is only used to describe the speed of
O>>>>> something like heart rate, the speed at which
O>>>>> the heart beats.

F>>> About rate, I think its use here is correct AFAIK but maybe
F>>> I'm wrong.

P>> In vernacular English, rate is always be used to describe the
P>> measured change in some parameter per unit of time.

O> Yes I was almost 100% sure the word rate could only be used when
O> speaking about *change* in some parameter. Therefore I was certain
O> that his use of the phrase fat rate was incorrect
O> precisely because I had asked him about his fat
O> percentage (which is the amount of fat he is carrying as a
O> percentage of his bodyweight)not how fast his body fat
O> was *changing* in either direction.
O> Maybe the French equivalent word for "rate" can be correctly
O> used along with the French equivalent
O> word for "fat" to mean fat percentage in French? I don't know,
O> but I do know that similar things confuse me sometimes when I
O> think about the equivalent Icelandic
O> words for some English words.

That's the case: in french "taux" can be translated in english
either by ratio or by rate

P>> However, that notion is
P>> generalized in calculus to signify the instantaneous change of
P>> any variable with respect to another with respect to which it has
P>> a dependency relationship (technically merely called
P>> a relation).
P>> Speed is merely one special kind of rate, the change
P>> of distance with time - even though speed is often
P>> incorrectly used for other types of rate (eg.
P>> reaction rate is sometimes, incorrectly, called reaction
P>> speed). Rates should never be expressed as percentages, since a
P>> percentage is merely a ratio of two measurements in the same
P>> units, of quantities with no necessary dependency except that
P>> one measurement (the denominator) is a
P>> part or super-part of the other measurement (the numerator).

Until this, I think I fully understand your reasoning, Paul:
If I say, my fat rate is 16.4 %: it's a wrong use
If I say, my fat ratio is 16.4%: correct use

P>> It would be
P>> correct to to apply the term rate to body fat if one used it to
P>> express the change over time of one's percentage or amount of
P>> body fat.

O> Thanks for the accurate explanation.
O>

Here I'm a bit puzzled; do you mean that I could say:
my fat ratio was 16.9% a year ago; it's now 16.4% so my body
fat rate is equal to (16.4-16.9)/16.9 =-0.0296 which means a
decrease of 2.96% of my fat ratio
If I understand your point, it is a correct use but of course nobody
states things like this regarding fat ratio.
(Moreover there is a reasoning error since 16.9% of 62.6 kg= 10.579
kg of body fat and 16.4% of 62 kg = 10.168 kg of body fat so my body
fat rate is (10.168-10.579)/10.579=-0.0389=-3,89% though my body fat
ratio has decreased of 2.96% (it is normal that the body fat rate
is lower than the decreasing of the body fat ratio since the body
weight has also decreased of 600 grams))
Maybe more interestingly than what I've wrote just above, these
calculations show that when I lose 600 grams of body weight, I lose
411 grams of body fat (and the remaining 189 grams must be water and
muscle)

P>> Perhaps it would be useful to post this dialog on rate,
P>> percentage and speed to Morelife Yahoo.
P>>

François Rose