Etymology
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obesity (n.)

"condition or quality of being corpulent," 1610s, from French obésité and directly from Latin obesitas "fatness, corpulence," from obesus "that has eaten itself fat," past participle of obedere "to eat all over, devour," from ob "about; because of" (see ob-) + edere "eat" (from PIE root *ed- "to eat").

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obese (adj.)

"exceedingly fat," 1650s, back-formation from obesity and in part from Latin obesus "fat, stout, plump," literally "that has eaten itself fat," past participle of obedere "to eat all over, devour," from ob "about; because of" (see ob-) + edere "eat" (from PIE root *ed- "to eat"). According to OED, "Rare before 19th c." Related: Obeseness. Latin obesus was translated in Old English as oferfæt "overfat." As Latin obesus also could be read as "eaten up," it also was used in a passive sense, "wasted away, lean."

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*ed- 

Proto-Indo-European root meaning "to eat," originally "to bite." 

It forms all or part of: alfalfa; anodyne; comedo; comestible; eat; edacious; edible; escarole; esculent; esurient; etch; ettin; fret (v.); frass; jotun; obese; obesity; ort; postprandial; prandial.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit admi "I eat;" Avestan ad- "to eat;" Greek edo "I eat;" Latin edere "to eat;" Lithuanian ėdu "I eat," ėdžioti "to devour, bite;" Hittite edmi "I eat," adanna "food;" Armenian utem "I eat;" Old Church Slavonic jasti "to eat," Russian jest "to eat;" Old Irish ithim "I eat;" Gothic itan, Old Swedish and Old English etan, Old High German essan "to eat."  

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overweight (adj.)
"in excess of proper or ordinary weight," 1630s, from over- + weight (n.). Of persons, as a noun, "obesity" from 1917.
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bariatric (adj.)

"of or pertaining to obesity," 1976, from Greek baros "weight, a weight, burden," related to barys "heavy" (from PIE root *gwere- (1) "heavy") + -iatric.

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corpulence (n.)

late 15c. "body size" (either large or small, with adjective), from Old French corpulence (14c.) "corpulence; physical size, build," from Latin corpulentia "grossness of body," abstract noun from corpulentus "fleshy, fat," from corpus "body" (from PIE root *kwrep- "body, form, appearance") + -ulentus "full of." In English, the restriction to "bulkiness, obesity, largeness of body" began late 16c. Earlier it meant "corporeality" (late 14c.). Related: Corpulency; corpulentness.

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