I've read about it a few months ago in some "serious" newspaper but I can't remember - maybe search would help if you try to filter out garbage pseudo-scientific sites? They stated something like body binding certain metabolic byproducts with fat when it can't cope with the load to process them later (like eating sugary food right before sleep), and they get stored around belly. So most obese people likely carry decades of unfinished exhaust byproducts alongside having clogged internal lymphatic system, which can lead to "loads of fun" when they finally try to get rid of their fat.