To deceive is to exist, to exist, deceive! Truth is not a matter of not lying, but rather a matter of deciding how you lie, to whom, and the extent to which your lies cohere to that which is called fact. As you say, often your body lies for you, even if your mind wishes otherwise.
This paragraph is brilliant- you really sum the issue up.
Every human being lies, just about every time they interact with another human. (Barring some sorta telepathic hivemind, I guess.)
There a different kinds of lies, different sizes of 'em, but everyone uses at least some kinds.
Maybe you think you "aren't a liar" because you tell friends something you're ashamed of, or confess when you do something bad, or you explain that you aren't a natural redhead- well, that's silly.
When was the last time you told someone what you really thought of them? When was the last time you told [AUTHORITY/BOSS] that the reason you missed your appointment was because you're a lazy shite? When was the last time you gave someone an actual answer when they asked "how are you"?
Civilization would fall into ruin if not for lies. Imagine if lying was suddenly gone.
Imagine a man greeting his new neighbour with, "Hi, I'm Bob. I think your face is ugly, you seem like trailer trash and I totally want to sleep with your hot wife. Is that a toupe? How much do you earn in a year?"
How do you see that going...?
tl;dr: The entirety of any form of human civilization is built upon lies, and anyone who thinks they aren't a liar is lying to themselves. In addition, even without that belief everyone does lie to themselves anyway. This post is true, honest.