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By Michael Rothman

At 44, Jennifer Aniston seems to only get more radiant with age, and according to the actress, one of the reasons is that she avoids fast food.

"I'll never forget when [fiance] Justin [Theroux] and I were on a road trip and we were so hungry. The only thing around was McDonald's," the Aveeno skincare spokeswoman told New York magazine. "I think I ordered a Big Mac. Wow, my body did not react well to that!"

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The results were not good. Comparing the splurge to "putting gasoline in a purified system," Aniston, who sticks to an organic and natural diet, immediately felt sick.

"That just made my stomach turn," she said. "I think what you put in your body, as well as stress, is reflected in the quality of your skin."

Aniston also shared a few other secrets for young-looking skin.

"I can never stress enough to my friends that they must do as I do … hydrate, hydrate, hydrate!" she said. "Drink lots of water, get enough sleep, exercise and eat a clean healthy diet, whenever possible."