It still didn't make sense to me so I googled it and found,
"Kummerspeck is the name for excess fat gained by emotional eating – specifically, the excessive eating people do in times of stress or sorrow."
So it literally refers to the _fat_ (speck) someone gains by eating while feeling _grief or sorrow_ (kummer). Except that the specific word for fat they use is the word for _animal fat_ and in some instances literally means bacon. What an interesting word.