Is wearing panties under shapewear a common practice? Should you wear your underwear with your shapewear?
Let's see... The purpose of shapewear is to create a smooth, streamlined shape that seamlessly transitions into your outfit. Wearing underwear underneath might give you the opposite effect.
While you can do whatever makes you feel the most comfortable, many bodysuit style shapewear are made to feel like they're just a second skin and therefore, shapewear don't require underwear.
A lot of people like wearing Spanx without panties, and they were designed that way, but the owner says that about half of women actually wear panties with them.
With that said, bodysuits are a perfect 'base layer' and often come with a hole to facilitate going to the bathroom; which would not serve its purpose if you wore undies.
As you can see there isn't just one good answer to this question and basically, the choice is yours! If you feel more confortable with both underwear and shapewear, then go for it!