the phrase "10 pounds of shit in a 5 pound bag" refers to an obese, large or overweight person in the kind of clothing you would expect to see a track star, or a member or a swim team wearing while competing.
Jane - "What is Haneefa wearing?"
Jill - "I think she got lost in Marshalls and bought clothes from the children's aisle by accident. Either that or she's color blind and has some serious depth perception issues"
Jane - "Haneefa looks like 10 pounds of shit in a 5 pound bag."
Jill - "Right on!"