Not self-indulgent, sparing, refraining from something - especially food and drink.
Abstemious entered into the English language at about the turn of the 16th Century, deriving from the Latin word "abstemius". The original Latin word is a combination of "ab", which means "from" or "away from", and "temetum", which means "strong drink". Because of its origin, "abstemious" has been used to refer to keeping away from alcohol, but over the years it has come to refer more generally to self-restraint and moderation. The word is also etymologically connected to "abstain", which is also derived from the Latin but arrived into the English language earlier from France.
Abstemious is similar to "moderate" or "frugal", but has a stronger sense than those words, usually implying self-control and discipline on the part of the person described. Unlike "abstinent", which it is close to, abstemious is used to refer to a general attitude of self-restraint rather than the complete rejection of one particular thing
Here are a couple of examples of how you might use "Abstemious" in a sentence.
"Though a typically abstemious man, he could never resist the desire to overeat when there were free samples on offer."
"The monks of St. Bernard's Abbey practised an abstemious way of life, staying away from meat and eating a simple breakfast of oats and wild berries."