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4.
1) A term given to people who are very smart, and hold much knowledge.

2) A term given to people who only have food on their mind 24/7
1)Oh man, Sarah got another A+ on her calculus test, she is so mentally obese

2)John: Dude I´m dying for a cheaseburger.
Adam: Stop thinking about food! Your so Mentally Obese!
by gordura pura November 25, 2009
 
1.
To eat as much shit as you like and never put on any weight.
"Dude, your like, Mentally Obese or something"

"Yeah, ya jealous?"

"Damn straight"
by HotBitch January 02, 2006
 
2.
One who has/thinks they have a great deal of knowledge, but grossly overuses it.

Someone who, at a party, always finds people walking away from them muttering " What a loser. Doesn't he have anything better to do?" after quoting useless and/or inaccurate statistics to make him look more interesting.

A person that uses their knowledge/feigned knowledge to make someone feel inferior for no other reason than to feel intellectually superior.
Man at a party: "Discount our neighbors to the east and I think you'll find we've got a sleeping giant on our hands. A veritable sleeping giant."

Everyone else at the party: "What a loser. He is so mentally obese that there should be a Richard Simmons work out tape dedicated to him."
by Serendipidity August 11, 2011
 
3.
Eating lots and always wanting food but not looking physically fat.
"Wow hes eaten 6 donuts and still eating more, hes mentally obese man.
by J.56 September 12, 2009