Buckle Up
When people (mostly females) have gained enough weight or gotten old enough that the size of their lower abdomen causes their belt buckles to point upward towards the sky instead of out as it normally would on a slim person. Women sometimes carry their extra body mass in the form of a "pocket" or "bubble" and their pants cover this "pod." Since women wear their pants higher than men due to their body structure, their belts sit atop of this globule and cause the bult buckle to point upward. 

Things are very bad when this sac is bigger than a woman's breasts. 

Things are very, very bad when you cannot even see whether a woman is experiencing Buckle Up due to their belt buckle being sandwiched under their huge breasts and above their balloned abdomen.

CAUTION: Buckling Up can cause blindness! There is record of people losing their eyesight due to the sun's rays reflecting off of a belt buckle and shining into someone's eyes.
"Wow, Jane has gained so much weight that she really has started to buckle up."