While the post had amassed 170,000 likes, some people were not so enthralled, saying the statement could be "triggering" for those battling eating disorders.
"One day of eating good food and enjoying tradition with your family and friends won't change your body. And even if it did … is it bad to be anything but slim?" one person ranted.
Another person argued: "Hey @sarahmgellar I freakin love you, but this messaging (esp for young vulnerable girls) is crap. What about someone who can do both?
"What about considering your messages through a body-shaming/adding to shitty culture filter before posting? Your body is gorgeous, but so are all bodies — chubby, fat, curves need lifting up, not more demonising."
But Gellar had staunch support from some of her celebrity mates, with Debra Messing writing: "Are you KIDDING ME!?!", while Shannon Doherty left a string of flame emojis.
Gellar — who has two children, Charlotte and Rocky, with husband of 16 years Freddie Prinze Jr — is the co-founder of Foodstirs, a brand that sells baking kits, and wrote her first cookbook Stirring up Fun with Food in 2017.
Clearly she won't be going back for seconds come Thursday.