The Silver Age of comics were a marvelous age of gimmick stories, and none followed this so well as DC comics: the writers and artists of their considerable super-hero line (the only real game in town in the fifties and early sixties) were fond of physically messing with their heroes: transforming them into the physical antitheses of their heroic selves. Nearly every one of the major super characters in the line (Superman and Boy, Wonder Woman, etc.) was consequently made fat for the purposes of a story, but the greatest of the era's transformations has to have been that which was experienced by The Flash.
The Silver Age Flash was Barry Allen, a police scientist in Central City with the power of super speed. As rendered by Carmine Infantino (who would later go on to oversee the entire DC line), Flash stories were models of forward motion, characterized by long horizontal panels, hands pointing the way to the next page and typically slender characters. Given the DC style, it was probably inevitable that one of the line's writers would temporarily change the Fastest Man Alive into the Fattest (after all, it only takes one letter change). Though you can see Infantino struggling with his rendering of his formerly lithe hero, the story and images remain enjoyable - a treat, one hopes, for female fat admirers.
Patrolling Central City in search of Gorilla Grodd, the Flash is unaware that the super-villain has developed a nefarious new weapon to rid himself of his "pesky enemy" forever.
Grodd's weapon (a ray gun developed through "startling new scientific principles") expands the scarlet speedster to half-ton size. To add insult to injury, he uses his super-powers to erase Flash's identity from his mind.
Disguised as a human named Dawson, Grodd sells the befuddled Flash to a circus sideshow, where he is ridiculed by the unknowing rubes.
A chance glimpse of himself in the Hall of Mirrors is enough to spark our hero's tampered memory.
Flash hies himself to a conveniently nearby dehydration plant where he - um - plants himself among the drying potatoes.
Though he's lost his excess poundage, our hero pretends to still be fat, so he can "surprise" the villain responsible for his short-term obesity. Brandishing a pin, he quickly punctures his ballooning uniform and captures the disguised Gorilla Grodd - thus ending the Flash's career in the big top.