Kim Zolciak Says Daughter's Butt Is Real Deal

Kim Zolciak is coming to daughter Brielle Biermann's defense denying the 19-year-old has ever had butt implants, despite what the Internet thinks.

Brielle posted a racy pic of her rump on Snapchat and many jumped to the conclusion that it was fake since she has posted video of her lip injections in the past.

However, Kim tells TMZ the proof Brielle's got natural cakes is in the rest of her body ... there isn't an ounce of fat to use for butt implants. Kim says Brielle's big ass comes from the gym -- she works out a ton.

Not to mention ... she's 19.