[com2kid]

American here, only every heard it meaning someone who likes fancy food.

Never heard of it being a fat person, except in so far as the word is old fashioned enough to conjure the image of a fancy dressed fat person eating fancy food.

[JackFr]

I have lived in the United States for all of my 59 years and have never heard or seen it used as meaning anything other than glutton.

Which is really no better evidence than you offer.

[stasomatic]

Same. "Gourmand" has always been linked to "gourmet" in my brain. However wrong according to the "dictionaries", I've seen it mean the same in colloquial use in a couple of languages I'm familiar with.