Como dizer "Avantajado (maior que o comum)" em inglês

Perhaps, in a (kinda) polite way he was with a with "his belly jutting out a little" or with a "prominent belly" (that sometiems not so polite, so be careful...).

Both in the first and the second case (the one of "corpo avantajado") could be "she is a big girl" or a big big girl, or still "big boned" or "stocky" etc. A slightly larger/ample person would be called well-rounded, plump, chubby, etc. Still to refer to an overweight person but not obese.

Also:

- Generously proportioned

- Bulky, (adjective (bulkier, bulkiest) 1.1 (Of a person) heavily built.)

- Huge, ((Extremely large; enormous.)

- Stout, (adjective 1. (Of a person) rather fat or of heavy build.)

Ex.:

• - A generously proportioned woman in a voluminous robe ambles [walk or move at a slow, relaxed pace] up and takes my ticket. miamiherald.com
  
  - Sure enough, when the door opened, the big, bulky man who entered was wearing a Roman collar. time.com
  
  - Witnesses reported that a bulky man in black threw a grenade-like object into the crowd, and then apologized to people next to him. time.com
  
  - Then a huge man with gold teeth and a rottweiler came out of nowhere. guardian.co.uk
  
  - A stout man who makes constant, self-deprecating references to his weight, the sheik is an avuncular * figure, popular with his students. nytimes.com

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* Avuncular, (port. Avuncular. 1. Relativo ou pertencente ao tio ou à tia materna. dic. Aurélio)
1. Kind and friendly towards a younger or less experienced person.
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(Definições em inglês do ' oxforddictionaries.com ')