06/22/2010 05:12 am ET Updated May 25, 2011

Simon Cowell's Fiancee Mezhgan Hussainy Counts His Calories

Simon Cowell's skinny fiancee has put him on a strict diet to get ready for their wedding. After a five-week detox of just veggie smoothies and one protein-based meal a day, Simon has reportedly already lost 12 pounds.

"I am vain. I'm obsessed with my weight," he said. He has also cut his 40 cigarette a day habit down to 15.

In Touch Weekly reports:

Simon Cowell is trying to get in shape for his upcoming wedding to fiancee Mezhgan Hussainy. Having dinner at Cecconi's restaurant in West Hollywood on April 8, Simon and Mezhgan each had a green salad, and then they split a fish entree, avoiding the pastas and desserts. A friend reveals that Simon has been counting calories with Mezhgan's help. "They're getting married this summer, and Simon wants to look his best," his friend explains. "He's losing weight, and Mezhgan is showing him how to do it."