LOS ANGELES - Moviegoers who tuck into a medium popcorn and a soft drink could be eating the equivalent of three McDonald's quarter-pounder burgers topped with a dozen scoops of butter, according to a US study.

A laboratory analysis of snacks sold at US cinemas and commissioned by the Center for Science and Public Interest (CSPI) found a medium popcorn and soft drink contained 1,160 calories and three days' worth - 60 grams - of saturated fat.

"Who expects about 1,500 calories and three days' worth of heart-stopping fat in a popcorn and soda combo? That's the saturated fat of a stick of butter and the calories of two sticks of butter," said CSPI senior nutritionist Jayne Hurley in a statement.

"You might think you're getting Bambi, but you're really getting Godzilla."

She said even sharing a small portion of popcorn between two people would mean consuming a day's worth of saturated fat, the kind that clogs arteries and is linked to heart disease.

Hurley said every tablespoon of "buttery" oil topping adds another 130 calories according to the study published in
Nutrition Action Healthletter.

"Asking for topping is like asking for oil on French fries or potato chips," she added.