Nutrition Nazi 

Someone who insists on getting in everyone’s face and insulting and belittling them on their food choices.

“Oh, girl, I just watched a Nutrition Nazi rip some poor girl a new asshole for having a carton of non-soy milk in her cart at the grocery store!”

Nutrition Nazi by Brett Burkhardt April 27, 2008

Nutrition Nazi 

A person described as being overly critical of other people's meal choices. Nutrition Nazis will often express their displeasure with someone's choice of food that they deem unhealthy or unfit for human consumption. Some might even advocate for everyone to be forced to have their meals meet the Nutrition Nazi's standards.

Father: You know, I heard that teachers are taking away kid's lunches because they thought it wasn't healthy enough.
Mother: Really? Those people are total Nutrition Nazis!

Nutrition Nazi by Gladilay May 1, 2017