“Seconds count— especially when dieting”

“Seconds count—especially when (you’re) dieting” is a pun upon the word “seconds” (meaning “second helpings” or “second servings”). The jocular saying has been cited in print since at least 1962.
 
A similar pun on the word “seconds” is “It’s not the minutes at the table that make you fat—it’s the seconds.” A different “seconds count” saying is “When seconds count, the police are only minutes away.”
       
 
Google Books
Apples of Gold
By Jo Petty
Norwalk, CT: C.R. Gibson
1962
Pg. 84:
Seconds count, especially when dieting.
 
1 February 1964, The Oregonian (Portland, OR), sec. 2, pg. 1, col. 1:
Seconds count, especially when you’re dieting.  J.H.
 
Google Books
Complete Speaker’s and Toastmaster’s Library
Edited by Jacob Morton Braude
Englewood Cliffs, NJ: Prentice-Hall
1965
Pg. 57:
Seconds count— especially when dieting.
 
4 February 1970, Waterloo (IA) Daily Courier, “Northeast Iowa People and Places” by John Barbour, pg. 17, col. 1:
Seconds count—especially when you’re dieting.
 
1 April 1981, Chicago (IL) Tribune, pg. A1:
Smile
Seconds count—especially when dieting.
   
Payson (AZ) Roundup
Senior Center Hosts Two Performers This Week
By Carol Zebb
Tuesday, August 4, 2009
(...)
Think about it: Seconds count — especially when dieting.