Take it easy.
What if you ate so much on Thanksgiving that you felt like you were going to burst—and then you actually did? How much food would it really take?
Well, as luck would have it, Mary Roach, the author of Spook, Bonk, and Packing for Mars, explored the topic in an essay for Salon in 1999 called "Unhappy Meal" that's worth revisiting in anticipation of our most gluttonous holiday. In it, she reports that our stomachs appear to have a capacity of about a gallon and in looking at old medical literature, she finds that there are only a couple of instances when you're at risk.
One, if you’re a prisoner of war or you've been stuck at the bottom a mine in Chile, suffering from a starvation diet, then loading up on carbs can cause the body to rapidly produce insulin, which disrupts electrolyte balance and can stop your heart.
Two, even if your stomach bursts from binging on 19 pounds of food, it doesn’t really pop open. It merely ruptures and floods the inside of your body with bacteria, creating a giant systemic infection which then kills you fairly quickly. Roach writes, "Bulimics make up the preponderance of stomach rupture deaths recorded in medical literature, second only to dogs and followed closely by the mentally retarded."
Three, if you've packed away way, way too much food, do not take Alka-Seltzer. One woman who ate "macaroni, meatballs, cheese, tomatoes, potatoes, bread, pie, three glasses of grape juice and several shots of whiskey" took some bicarbonate in water and her stomach burst. Here's what it looked like:
Illustration from William T. Lemmon and George W. Paschal, Jr.'s "Rupture of the Stomach Following Ingestion of Sodium Bicarbonate," published in the December 1941 issue of Annals of Surgery.