You're describing it backwards.

Obesity tends to cause heart enlargement (https://radiopaedia.org/articles/obesity-cardiomyopathy), larger muscles (as you're doing essentially built-in weight training just walking around), and organs don't tend to shink; cross-sections show a pretty similar body cavity (https://www.cultofweird.com/medical/human-body-slices/) - the fat largely goes on top of it.