The developer of Grape-Nuts utilized a public relations survey in which 4,500 out of 5,000 doctors recommended eating breakfast to market the essentiality of breakfast.
"The guy who developed Grape-Nuts, he had a really good PR person who then did a survey with doctors. Out of 5,000 doctors, 4,500 said, "Yeah, you probably need breakfast." And so then they used that: nine out of 10 doctors, or 4,500 doctors, recommended breakfast, so you should eat a breakfast as well." (said at 0:48:30)
No published record matching the claim that the developer of Grape-Nuts conducted a survey of 4,500 out of 5,000 doctors to market breakfast was located; this does not prove the claim false.
contradicted by web sources
The famous survey of approximately 4,500 out of 5,000 doctors endorsing a hearty breakfast was orchestrated in the 1920s by public relations pioneer Edward Bernays on behalf of the Beech-Nut Packing Company to promote bacon, not by the developer of Grape-Nuts. While Grape-Nuts (made by General Foods) later ran ad campaigns emphasizing that breakfast is "the most important meal of the day," the physician survey strategy belonged to Beech-Nut's bacon campaign.