Diet: (Noun) A special course of food to which one restricts oneself to lose weight.

If you thought Katie Holmes achieved that gaunt look of hers just from a grueling work schedule, taking care of a toddler and Scientology brainwashing; think again! She's got a little secret: The calorie burning diet drink Celsius!

The actress’s bodyguard was pictured holding the soft drink for her as she signed autographs for fans outside the Gerald Schoenfeld Theatre in Manhattan where she has been performing in the Arthur Miller play All My Sons.

Celsius, Holmes's drink of choice, contains a ‘thermogenic blend’ which increases metabolism in order to burn calories, each bottle contains less than 10 calories and its makers claim that it can burn up to 77 calories over a three to four hour period. (Source)

Then again, how do we know that the Celsius is definitely for Katie? I mean, I know she's technically a toddler and everything, but Suri's cheeks have been looking a bit chubby lately. Maybe those little Burberry dresses she wears were starting to get a little tight, eh? That'd hardly be the result of a growth spurt. I'm pretty sure "growing" is one of those human functions that Sceintology doesn't believe in.

More of Katie walking around NYC a few weeks ago: