The funnyman admits he lost 35 pounds (15.8 kilograms) as he prepared to play the British actress' fiance - and a trainer/nutritionist was hired to monitor his calorie intake on the set.
Segel says, "I was told that it had to be conceivable that Emily Blunt would ever choose me to be her husband... They (producers) sent a trainer to the set and I had to work out twice a day and then he would watch me eat all day."
But the actor found a way to cheat during the shoot - so he could nibble between takes: "I play a chef in the movie and so there are a lot of scenes where I had to eat. I was paying my co-stars phenomenal amounts of money to mess up their lines during the scenes, so I would get to keep eating."