This is a phrase (if memory serves me right, and i will check) it was Lays maybe even before Frito’s became Frito Lay. It was cute and catchy and its purpose was to make you think, by mental manipulation, you cannot stop eating their product. It is meant too, to physically addict you, salt refined sugars and fat (and yes even glutamines).
What is perplexing is that in all the data that has been presented that being obese is correlated (and of course i said correlated not causes, though in my heart i think it is causality) with western diseases, which continually plague americans: heart disease, diabetes, arthritis, immune disorders.
What is different about today’s diet is that it is consumed without regard for what is necessary, and what is healthful. It is consumed because someone knew you would eat it, because they stacked the cards against 
you, they added all those things which make you eat more than one. Shame on big food companies.
I wonder if they are in ca-hoots with big pharma… afterall the obesity epidemic spikes the western diseases and no one wants to “eat just one” so they would rather “take a pill” than get their behinds off the sofa and run around the block, or heaven forbid, take up a sport that takes some energy and coordination and teamwork.
WHo is to blame for the obesity epidemic? Well ultimately it is the consumer, but the consumer has to have iron-will to avoid what is deliberately out there to addict him.
I googled “bet you cant eat just one” and up came 4 million posts. not-so ha ha.
Here is some real science
DiPatrizio NV1, Astarita G, Schwartz G, Li X, Piomelli D. Endocannabinoid signal in the gut controls dietary fat intake. Proc Natl Acad Sci U S A. 2011 Aug 2;108(31):12904-8. doi: 10.1073/pnas.1104675108. Epub 2011 Jul 5.
Abstract begins thusly: “Oral sensory signals drive dietary fat intake, but the neural mechanisms underlying this process are largely unknown.”
Reposting one site: soleiletoile/flickr read it here
In his book, “The End of Overeating,” former FDA commissioner David Kessler charges food companies with deliberately manipulating the chemical composition of their products to make them addictive to people with vulnerable brain chemistries— i.e., children. Kessler participated in subsequent research that found similarities in how rat’s brains experienced withdrawal symptoms similar to drug withdrawal then, after being fed by a high fat, high sugar mix, they were suddenly put on a diet. The food industry dismissed Kessler’s claims by ignoring them, and one of their top lobbyists admitted that the strategy was deliberate: to respond would call attention to the claims and force the good companies into a tit-for-tat debate about neuroscience. Kessler believes that many food companies ought to be publicly shamed for constructing and marketing addictive, unhealthy food to kids.