The love of his life that he had known for six months, and cheated on her three months ago.

From the Defector link:

It is not my place to tell this anonymous Norwegian woman what to do with her life. I will simply note that I have found it in my heart to forgive people who never medaled in anything. Does Lægreid seem like the sort of person who will learn from this mistake and dedicate himself to the rigorous introspection and honest self-accounting that it requires? No, not really. He seems like a fairly selfish moron who follows every heedless whim. But winters are long and brutal in Oslo, and I certainly would not judge how anyone decides to keep warm.

No cause of death has been released for Guttorm Bakken. He died in his hotel at the training camp in December at the age of 27.