Credit: Instagram

What a difference a few years can make, right?! It feel like just yesterday Catelynn Lowell and Tyler Baltierra were little high schoolers welcoming a baby into the world on 16 and Pregnant. Nowadays, these crazy kids are all grown up and looking better than ever thanks to a combination of fab genes and a serious workout routine.

It's no secret that Catelynn hits the gym a few times per week to maintain her rockin' post baby bod, but Tyler's also got a bout of fitness fever. The 21-year-old has been focusing on bulking up (we know, boy probs) and his hard work is certainly paying off.

On April 15, Tyler posted a shirtless pic to Instagram, flaunting his beefed up frame. "Afternoon workout! #grindtime," he wrote. Lookin' good, T!

And if you're thinking Tyler seems a bit more bronze than usual, you're right! The soon-to-be married couple spent the past month in Los Angeles filming the upcoming season of VH1's Couples Therapy, which will most likely air sometime this fall.

Are you impressed with Tyler's progress? Tell us below, Teen Mom fans!