Vain

as in

"I’m not vain."

Variations: "I’m the least vain person I know ... You’re so vain ... How can anyone be so vain?"

The key point here: it is not "vanity" to be concerned about hair (at least his hair), smiles, profiles, biceps, or stomach muscles. According to him, that is. In short, by some mysterious alchemy, the aspects he cares about lie outside the scope of "self admiration". They are things that it is "only sensible" to pay attention to, the same way that it is "only sensible" to monitor your blood pressure and pulse.

When he fiddles with his hair, tossing it this way and that to cover some bald spot or strokes his pate to make sure it is perfectly smooth, he isn’t being "vain", he’s carrying out a health check-up. Making sure he isn’t about to catch cold or perhaps have a heart attack because some strand is out of place.

Whereas if you so much as open a pocket mirror to get a lock out of your eyes, that’s "vanity".

If he cocks his head in a strange way, narrows his eyes and twists his lips into what he thinks is a James Bond look, often when some young filly has just caught his eye, he isn’t being "vain", he’s making sure that his head is still screwed on and that his facial muscles work.

If he passes a mirror when he is out for a walk and pauses to examine his posture, sucking in his stomach and clenching his fists to swell his biceps, he isn’t "vain", he’s guarding against a lethal stoop or paralysing sag. Whereas you, according to him, you waste your time on such trivial matters as keeping your
eyelashes uniform, your skin tone warm and your clothes neat. Oh, silly you! Why can’t you be more natural, as he is.

As for any anxiety over the hint of laugh lines in your face or expansion in your posterior - an anxiety which he shares (indeed, shares enough to helpfully notice other better endowed girls as role models) - that too is "vanity". He’d expect you to do something about it, sure, but without expressing any worry. One interesting idea: tell him he has some new facial flaw, a spot or tic, and watch him dash off
terrified to check it.