Visceral

When:

Lookups spiked on November 29, 2012.

Why:

A widely reported new medical study revealed that deep belly fat in men – called "visceral fat" – is a risk factor for bone loss.

Visceral means "of or relating to an internal organ of the body." It comes from the Latin word for "internal organs."

(If you're curious about terms for other kinds of fat – including brown, white, and subcutaneous – there's more information here.)

Visceral is often used metaphorically to mean "coming from strong emotions and not from logic or reason" – or, to put it another way, "instinctive."