The actress says she often ignores her healthy eating plan and gorges on calorific treats.
“My big holiday secret is so great and it works,” she said. “What I do is to eat before I go to a holiday party.
“I go with a full stomach of like fish or veggies or whatever it is I have at home that is good, and then when I get to the party I will probably have a little nosh on something but it’s not going to be disastrous.
“But I have to admit if I falter on my healthy eating I really falter. If I go, I go hard.”
Eva has previously revelaed how she works her butt off to stay in shape.
“There is no real secret to getting in shape for me,” she said earlier this month. “I just work really hard. I work my buns off but every time I wrap I have a full pizza.
“I ask everyone if they want pizza too — but they can’t share with me because that one is all mine.”