Often, saddlebags. excess fat around the hips and buttocks.
Not sure if you know this but the term saddlebag can be endearing. At least in my family it can be. Although it can be quite insulting at the same time. This is the name my sisters, brother and I call each other. "Hey Saddlebags! How's it going?" Or simply: "See ya, Bags." It stems from the movie Ace Ventura: Pet Detective. Ace (Jim Carrey) says at one point "Well, why don't you cry about it. Saddlebags."
Fast forward a few years, I live in Seattle, one sister in Boston, the other sister and brother in our hometown. Someone (I think Maddy) deemed me a Seattle or Seaddle Bag. So now I am (lovingly?) referred to as a Seaddle Bag.