As holiday parties continue to fill your calendar this month, Us Weekly turned to celebrity trainer -- and star of ABC's The Revolution -- Harley Pasternak, to help demystify the hidden dangers of seasonal cocktails.

"The dangers of the bar at a holiday party are many: Sugary drinks, high-alcohol beverages and quite often, little ornamental foods that are placed in those beverages," says Pasternak, adding that the caloric value of drinks like a martini with olives -- a healthy fat -- are especially high. "Add up all those drinks you ordered 'dirty' and before you know it, you've gained three or four pounds just from olives."

For more of Pasternak's tips on how to navigate the holiday party bar, check out the video above. In January, the trainer will serve as one of the cohosts on ABC's new transformation series, The Revolution.