“Don’t dig your grave with your own knife and fork” is a food saying that has been printed on many images.
 
     
Google Books
April 1921, The Birth Control Review, pg. 18, col. 1 ad:
Are You Digging Your Grave With Your Knife and Fork?
(Truth Publishing Company.—ed)
   
Google Books 
The Macmillan Book of Proverbs, Maxims, and Famous Phrases, Part 1
By Burton Egbert Stevenson
New York, NY: Macmillan
1948  
Pg. 965:
With his knife and fork he digs his own grave.
 
Google Groups: rec.food.cooking
Request: A recipe for REAL demiglace
Wilfred
9/18/97
(...)
Don’t dig your grave with your own knife and fork.
English Proverb
   
Google Books
QPB Encyclopedia of Word and Phrase Origins
By Robert Hendrickson
New York, NY: Facts on File
1998
Pg. 203:
digging one’s grave with a knife and fork. This humorous expression for gluttony was first recorded in England during the late 19th century and is still occasionally heard there and in America in these weight-conscious days.
 
Google Books
Prescription for Dietary Wellness:
Using Foods to Heal
By Phyllis A. Balch, CNC
New York, NY: Penguin Groups (USA) Inc.
2003
Pg. 210:
Don’t dig your grave with your own knife and fork. — English proverb.
     
OCLC WorldCat record
Quit digging your grave with a knife and fork : a 12-stop program to end bad habits and begin a healthy lifestyle
Author: Mike Huckabee
Publisher: New York : Center Street, 2006, ©2005.
Edition/Format:   Print book : English : 1st trade ed
Summary:
“With his new 12-STOP program, he encourages readers to break free from the destructive habits that threaten their health and esteem. According to Huckabee, focusing solely on weight loss usually leads to failure. Attention to total body health is the only way to truly succeed”—Amazon.

Google Books
It’s Always Darkest Before the Fridge Door Opens:
Finding Joy in the Cold Places of Life
By Martha Bolton and Phil Callaway
Baker Publishing Group
2006
Pg. 112:
Don’t dig your grave with your own knife and fork.
English Proverb
 
Twitter
Supreme Skin
@FitCoachCarole
Here’s what they say…“Don’t dig your grave with your own knife and fork.” 
~ English Proverb http://www.yourfreedom123.com
10:56 PM - 30 Aug 2008
 
PhenQ
100 motivational weight loss quotes to keep you inspired
January 16, 2018
(...)
Don’t dig your grave with your own knife and fork.