Wiegratz was born in Magdeburg, Germany. He is known for his 2005 portrayal of the greedy Augustus Gloop in Charlie and the Chocolate Factory. He went to a casting call not being sure of receiving any particular part, but caught the attention of a casting director and was placed on a shortlist for the role of Augustus. Wiegratz returned for several callbacks and eventually received the part, which marked his English-language film debut and also required him to wear a fatsuit instead of getting fat on his own terms. He performed his own stunts in the scenes of Augustus falling into the river in Wonka's Chocolate Room.