It seems the reason Super size Me documentarian Morgan Spurlock gained all that weight during the 30 days he consumed nothing but McDonald's wasn't because he ate too much Golden Arches — but because he didn't eat enough.

Science teacher John Cisna of Ankeny, Iowa, decided to repeat Spurlock's infamous experiment, but rather than subsist for an entire month on just Mickey D's, Cisna went in for an extra two.

At the end of the three-month challenge, Cisna discovered something super surprising: He was healthier than before.

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Not only had he lost 37 pounds, but his cholesterol took a significant dive, from 249 to 170.

Cisna's secret was that, rather than gorge himself with whichever menu item caught his eye, he made careful selections, and never surpassed 2,000 calories per day.

He also took up walking as a form of exercise.

"I can eat any food at McDonald's (that) I want as long as I'm smart for the rest of the day with what I balance it out with," said Cisna, who also turned his McDiet into a documentary. "The point behind this documentary is, 'Hey, it's (a) choice. We all have choices. It's our choices that make us fat not McDonald's."

[video via KCCI]