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Irresistible! By all accounts, Jessica Simpson looked gorgeous during her wedding to new husband Eric Johnson -- and prepared for weeks to be wedding-ready.

A source tells Us Weekly exclusively that the singer-turned-designer, 33, switched up her eating habits in the days before her July 5 nuptials. "Jessica did a vegan diet for about two weeks leading up to the wedding," the source says.

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Simpson's vegan kick follows those of other superstars who have done the same, including Beyonce, Jay Z and Jennifer Lopez, who dropped a few pounds while on the 22-day vegan challenge.

Looking better than ever with her healthy body toned and strong, Simpson seems to have benefited from the restrictive diet. She famously lost about 60 pounds while on Weight Watchers earlier this year, after the June 2012 birth of her son, Ace.

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The vegan munchies weren't the only nutrients Simpson added before she said "I do"—the source tells Us that she "also got quite a few B12 shots."

For her skin, Simpson "opted to get sugar dermabrasion on her face," the source tells Us, adding that she chose sugar over salt "so it would be less harsh."

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The second-time bride was just as exacting with her style choices, picking a custom-made Carolina Herrera gown for her wedding. She wore the specialty number for her vows to Johnson, 34, which took place at the San Ysidro Ranch in Montecito, Calif.

The swanky affair hosted 250 guests, including some familiar faces such as Jessica Alba, Topher Grace and Donald Faison. Simpson and Johnson are now officially husband and wife after four years together and the births of their two children, daughter Maxwell, 2, and son Ace, 12 months.