The adjective abstemious is someone who avoids doing something too much enjoyable such as eating food or drinking alcohol.

Synonyms are abstinent, restrained, austere, or frugal.

The word origins from Latin abstemius meaning “sober, temperate, abstaining from wine” and assimilated form of ab “off, away from” and stem of temetum meaning “strong drink” which is related to temulentus meaning “drunken”. 

She was very abstemious when it came to eating because she was determined to achieve that summer body with the diat.

I admire people who are abstemious eaters and drinkers.

Their family is known to be abstemious.