A “gut bomb” (or “gutbomb” or “gut bomber”) is any food the “bombs” your “gut.” Originally, a “gut bomb” was a greasy hamburger, but not one of any particular place. ‘Gut bomb” has been used to describe hamburgers at White Castle and Krystal. The term “gut bomb” has been expanded to mean any food that’s unhealthy.
   
“Up in Columbia Heights high school, said Ray Carlson, cars are bombs and hamburgers are gut-bombs” was printed in the Minneapolis (MN) Morning Tribune on October 24, 1955.
   
   
everything2
Gut bomb
(thing) by funky49
Wed Oct 03 2001 at 16:09:15
A gut bomb is food that causes a disturbance in the midsection. At the very least a gut bomb causes a stomachache, but also may include diarrhea or heartburn. Popular gut bombs are primarily creamy foods like a rich dessert or greasy foods like chicken wings, hamburgers, french fries, Pizza Hut pizza and buffet style Chinese food.
 
Usage: “That medium-rare chili-burger with extra cheeseand bacon and cheese fries was a real gut bomb!”
 
Be kind to your stomach. Gut bombs may be avoided by not eating too much of the offending food, drinking extra water or staying away entirely from the foods that make your belly gurgle in digestive pain.
 
For the liquid equivalent of a gut bomb, see bladder missile. 
 
Urban Dictionary
gut bomb
A coney dog or chili dog, LOADED! Occasionally misused to also describe one of them bite sized late-night “greezy spoon” hamburgers with grilled onions, which technically is known as a “slider.”
After the bar closes let’s stop on the way home and get a six-pack of gut bombs.
by gumby Apr 16, 2003
   
(Historical Dictionary of American Slang)
gut bomb n. a greasy hamburger; (broadly) any food considered to be especially unhealthy. Also gut bomber.
1969 Current Slang I&II 46:

, n. Hamburger.—College males, SOuth Dakota.
1980 Grizzard Billy Bob Bailey 27: “Gutbombers,” those little hamburgers that used to cost a dime and now cost thirty-five cents.
1987 Knoxville, Tenn., man, age ca30: Let’s go for some gut bombs.
1989 J. Walter Defcon One 122: Doherty complaining about…“gut bomb” doughnuts destroying his appetite.
a1990 Poyer Gulf 187: Gut bombs and grease sticks.
   
24 October 1955, Minneapolis (MN) Morning Tribune, “‘Hot Rod ‘Slanguage? It’s Crazy, Man, Crazy” by Peg Johnson, pg. 27, col. 1:
“C’mon, big man, you wanna buzz out?” asks she.
 
“OK, doll. Let’s lam this joint and whip on over to Joe’s. I could dig a gut-bomb right now,” answers he.
(...)
For those who don’t, here’s the translation: Seems this doll—ooops, young woman—would like to take a ride in her young gentleman friend’s car, and he agrees, feeling the need of a hamburger anyway.
(...) (Col. 5—ed.)
Up in Columbia Heights high school, said Ray Carlson, cars are bombs and hamburgers are gut-bombs.
   
1 June 1968, The World (Coos Bay, OR), “Slang—Not So Way Out,” pg. 4, col. 1:
GUT BOMB—Food (Hamburger).
 
22 November 1969, San Mateo (CA) Times, “Large Game Day” by Ron Reid, pg. 24A, col. 2:
On any other occasion, say in the sumptuous dining room of the Bide-a-Wee Gut Bomb Drive-In, the guy would have hit the ceiling and immediately filed suit for the cleaning bill, acute emotional trauma and damages for invasion of privacy, since he was deftly hugging a curvaceous co-ed by his side.
   
19 April 1972, Capital Times (Madison, WI), pg. 19, col. 1:
ANYWAY, I had just passed a bunch of cops chowing down on gut bombs and fries in front of McDonald’s when I reached the intersection of State and Lake,...
   
8 July 1974, Capital Times (Madison, WI), “Cookin’ with Fred,” pg. 20, col. 1:
How to Make Egg Noodles Stroganoff with Beef-Like Chunks (a quick-serve dietary substitute for the usual meagre fare of countrified carry-out chicken, fresh frozen pizzas, and gut-bomb drive-in hamburgers):...
   
Google Books
The Finely Fitted Yacht
By Ferenc Maté
Published by Albatross Pub. House
1979
Pg. 114:
I have not been able to ascertain precisely what the “worse” could be, but it sounds comparable to a steady diet of gut-bomb burgers, so it must be avoided at all costs.
 
23 May 1987, Atlanta (GA) Journal and Constitution:
When I was a sportswriter we used to call them “gut bombers” and the munchy little Krystal burgers are still one of my favorites.
       
Google Books
Gates: How Microsoft’s Mogul Reinvented an Industry—and Made Himself the Richest Man in America
By Stephen Manes and Paul Andrews
Published by Doubleday
1993
Pg. 129:
For lunch breaks Marla would run across the street to a hamburger joint for ‘“gut bombs” — real greasy hamburgers, on these little wax-paper kind of holders.
   
Google Books
International Directory of Company Histories
By Jay P Pederson, Tina Grant
Published by St. James Press, 1996
Item notes: v.12
Pg. 551:
White Castle hamburgers have such nicknames as Sliders, Gut Bombs, Castles, Whitey-One-Bites and Belly Busters, and in recent years, the company’s marketing team has capitalized on this image.
   
Village Voice (NY, NY) - Fork in the Road food blog
How Do You Spell G-U-T-B-O-M-B?
Posted by Robert Sietsema at 3:42 PM, February 5, 2009
(...)
How Do You Spell G-U-T-B-O-M-B?
Posted by Robert Sietsema at 4:42 PM, February 13, 2009