The “pinch test” (popularly called by the rhyme “pinch an inch”) is simply a pinch of flesh—usually performed at the waist—between the thumb and forefinger. If someone can “pinch an inch,” that has long been regarded as a sign that a person is overweight.
 
The term “pinch test” has been cited in print since at least 1952. The rhyme “pinch-an-inch” has been cited in print since at least 1960.
 
 
19 September 1952, Syracuse (NY) Herald-Journal, “Can Your Finger Pass In a Pinch?” by Ida Jean Kain, pg. 42, col. 1:
THE PINCH TEST which is used as a gauge of overweight is right handy for determining if there is too much fat padding the midriff.
 
The test is to take a deep pinch of flesh covering the lower ribs at the side of the torso. Pick up the roll of fat betwixt thumb and forefinger. if the span between thumb and finger is more than once inch across, that’s more or less solid evidence of excess fat padding.
 
The pinch test can also be applied to the waistline. Take a deep pinch at both sides of the natural waistline, picking up the fat between thumbs and forefingers. If you can pick up more than half an inch at both side of the waist…that’s a sign of too much fat padding the middle measurement.
 
25 May 1953, The Oregonian (Portland, OR), “Pinch Tests Spot Trouble: Bulging Waist Can Be Solved” by Ida Jean Kain, sec. 2, pg. 2, col. 3:
This pinch test tells…place your hands on either side of your natural waistline, with thumbs and forefingers encircling the waist area. See how much fat you can pick up on either side. If it is more than a half inch or three-quarters at the most…excess fat is padding the waist.
 
16 March 1954, Seattle (WA) Times, “Food Selection Is Reducing Key” by Dorothy Neighbors, pg. 22, col. 1:
Dr. (Frederick J.—ed.) Stare of the Department of Nutrition, School of Public Health, Harvard University, advises us to try the pinch test.
 
“Take a deep pinch just below the lower rib,” he said. “if the distance between your thumb and index finger is greater than an inch, it is mostly excess fat.”
 
Google Books
Reduce and Stay Reduced
By Norman Jolliffe
New York, NY: Simon and Schuster
1957
Pg. 13:
The third is the pinch test. The layer of fat beneath the skin varies in thickness in different locations, being the thinnest over the back of the hands and thickest over the abdomen. It is of a convenient thickness for your doctor to measure in several locations, but for self-measuring the best place is over the lowest rib straight down from the arm pits where the normal amount of fat is between one-fourth and one-half inch thick. The thickness of a double layer of skin and its attached fat can be measured by skin calipers, but it is usually sufficient to take a deep pinch of skin on the side of the body just over the lower ribs, between the thumb and index finger as shown in Figure 2. If the distance between the thumb and the index finger is greater than one inch, as in Figure 2a, there is probably an excess of subcutaneous fat.
 
Google News Archive
26 March 1959, The Spokesman-Review (Spokane, WA), pg. 7, col. 1 ad:
Are you overweight? The standard weight-height tables do not always give you an accurate answer. The “pinch test” is more reliable. Read about it in April McCall’s.
(Wesson Oil ad—ed.)
 
9 April 1960, Springfield (MA) Union, pg. 3, col. 1:
AIRMEN TOLD:
TRIM POUNDS
OR BE MOVED
“Pinch-an-Inch” Test De-
signed to Keep Troops
In Shape
WIESBADEN, Ger. (UPI)—“Take the pinch-an-inch test.” if you fail, slim or be shipped out.
(...)
The “pinch-an-inch” test is a fast and fairly painless way of testing for obesity.
 
If you can pinch an inch of fat on any part of your body, it’s time to start a diet, they said.
 
Google News Archive
6 November 1965, Pittsburgh (PA) Press, “‘Pinch Test’ For Overweight” by Josephine Lowman, pg. 5, col. 6:
There is also the “pinch test.” Pinch yourself on the back of your upper arm or on your abdomen. If you get an inch or more between your thumb and fingers watch out.
 
Google Books
For Men Only,
With a 30-Day Guide to Looking Better and Feeling Younger
By Jack La Lanne with Jim Allen
Englewood Cliffs, NJ: Prentice-Hall
1973
Pg. 76:
Can you pinch an inch? If you can, you’re officially fat. Congratulations.
   
Google News Archive
26 April 1977, The Gazette (Montreal, Quebec), “Get Fit” by Judy Gill, pg. 39, col. 4:
If you can pinch an inch of stomach fat you’ve 10 pounds to lose
 
Google News Archive
30 June 1977, St. Petersburg (FL) Times, pg. 30D, col. 1:
Pinch an inch tells “weighty” tale
United Press International
SAN FRANCISCO—You can’t beat the “pinch test” for finding out if you’re among the 20 per cent of Americans who are overweight, the American Medical Association (AMA) said at its annual convention.
 
The AMA offered this advice to those who wonder if they are among the chubby:
 
“Try the ‘pinch test.” Grasp the flesh just above you waist between your thumb and the tip of your forefinger.”
 
Then, said the AMA, “if you’re pinching more than a one-inch thickness,” it’s time to look at your toes to see if there’s an “unobstructed view.” You should also look at your scale and in the mirror.
 
Google Books
Stick Figure:
A Diary of My Former Self
By Lori Gottlieb
New York, NY: Simon & Schuster
2000
Pg. 96:
“If you can pinch an inch,” she says, “then you need Special K cereal.”
 
Google Books
Winning With One-Liners: 3,400 Hilarious Laugh Lines to Tickle Your Funny Bone & Spice Up Your Speeches
By Pat Williams
Deerfield Beach, FL: Health Communications
2002
Pg. 145:
It’s time to diet when you can pinch an inch — on your forehead.
 
fitsugar
When You Pinch an Inch of Flesh, It Isn’t Always Fat
THE SKINNY ON FAT: SHOULD YOU ONLY BE ABLE TO PINCH AN INCH?
Updated Sep 15 2010 - 10:48am · Posted Sep 15 2010 - 8:00am by Self
(...)
For one, says Comana, not everyone carries her weight in the same place, so you need to check a minimum of three sites (generally front of the thigh, right above the hip bone, and the triceps). Even then, without calipers and specific training, it’s impossible to know how much of what you’re grabbing is skin and how much is actually fat. Other factors also need to be considered, such as age and skin elasticity.