Back in the day when text was set by hand, leading was considered to the lead plates inbetween the lines of text.
The plates were available in many depths: 1pt, 2pt, 3pt, etc.
One of the most famous Swiss graphic designers Josef Müller-Brockmann who was professional typographer in his 1981 book "Grid systems in graphic design" also referred to leading as the vertical distance between at least two lines of text.
Now in CS, leading is considered to be a vertical distance between the baselines of the text and NOT the actual distance between the end of descender and the top of cap or ascender.
Therefore, leading is always bigger than the body size. For example, 16pt leading = 11 pt body + 5 pt of interline space.
So I wonder, why the meaning of the leading has changed? Is there a way to use the "original" leading in CS?
No, you can't change how InDesign uses its leading.
It seems the word "leading" itself has changed its meaning, from the original "interline distance" to the modern "baseline-to-baseline". You can read this *very* entertaining thread on Typophile for current insights: http://typophile.com/node/90717