Kim Zolciak-Biermann doesn't mince words when it comes to explaining how she's seemingly able to snap back into shape so quickly after giving birth.

The mother of six tells E! News that she gained 50 pounds both with baby No. 3, Kroy Jagger, and before delivering twins Kaia and Kane back in November—and it's quite interesting how the body works.

"I definitely think genetics play a role, that's number one," the 36-year-old Don't Be Tardy... star told E! News, sitting alongside hubby Kroy Biermann.

Kim Zolciak

Splash News

Number two," she continued, "I think with twins that every little morsel of food that you eat...goes to the baby. I made two human beings at the same time and I gained 50 pounds. Which I gained 50 pounds with KJ, so the twins, I think they took it from me."

"And," Kim admitted, "I do wear kind of like a homemade-type girdle after I had the babies, for six weeks, and I'm wrapped so damn tight for a period of time—and it makes your stomach flat as a board."

But there's no hiding in a bikini, and Kim has always been quick to show off her sexy-mom swimsuit bod—no small thanks to her diet, exercise and Xenadrine regimen.

The former Real Housewives of Atlanta star has acknowledged in the past that she was left with a hernia after giving birth to Kaia and Kane, and, while she admits that she's lucky to not have stretch marks or other visible post-baby issues, Kim did end up having to consult a plastic surgeon--which you'll see on Don't Be Tardy...'s third season, premiering July 17 on Bravo.

Watch the clip to find out why!

(Bravo and E! Online are both members of the NBCUniversal family.)

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