A Weber is a barbeque grill and has a rounded lid. Anyone who is fat with a big, rounded stomach is said to have "swallowed a Weber" because the round stomach resembles the lid of a Weber.
Look at Al, it looks like he's swallowed a Weber!
A Bentley Belt is a flotation device for kids that has a tube going around their abdominal area. In urban terms you would say someone is wearing a Bentley Belt because they are fat due to their waistline/stomach resembling a kid wearing a Bentley Belt.
Check that chick, she's wearing a serious Bentley Belt!