I'm fat. Know how many times this has mattered in an Open Source project? Zero. How many times I've been discriminated against at a conference? Zero. How many times I've had a patch rejected on that account? Zero.
It's bullshit.
So yes, I agree that no one should ever discriminate in Open Source based on weight. But also, no one should ever discriminate based on eyebrow length. (Mine are a bit weird.) Shall we write that in, too? How about people who tie their shoes with granny knots? How about people with red hair? And on, and on, and on.
None of this has any place in a CoC. And all such are slow acid eating away at the foundations of good will and civil behavior. Fuck that.