Ascetic

noun a person who abstains, especially from indulgence in alcoholic beverages; a teetotaler

• The abstainer refused to partake in the wine tasting event.
• She's always been an abstainer when it comes to alcohol.
• He's a total abstainer when it comes to junk food.
• Being an abstainer from social media, she enjoyed a more peaceful and focused life.

adjective showing self-restraint in eating or drinking; moderate

• The abstemious scholar only indulged in the occasional glass of water during long study sessions.
• My friend is so abstemious, he won't even have a slice of cake at parties.
• I can't believe how abstemious Jake is being, he usually drinks like a fish.
• Her abstemious approach to spending money has helped her save up for a dream vacation.