In the pics, Simpson rocks a multi-colored Mara Hoffman one-piece with cut-outs near her waist as she poses with one of hubby Eric Johnson's golf clubs. And while she might be sucking in her cheeks a bit -- duck lips, anyone? -- a person certainly can't "suck in" thighs to show muscles like she has.
"If I'm in a bathing suit I should pose proudly," she captioned the image shown above left, which was the second to go up. "Eric's driver," read the caption on the other, though we doubt anyone was looking at the club.
The 33-year-old fashionista and singer has been working out with celebrity trainer Harley Pasternak, who has also worked his magic on folks including Katy Perry, Amanda Seyfried, Megan Fox, Lady Gaga and Jennifer Hudson.
Simpson has famously been a spokeswoman for Weight Watchers since gaining a bunch of weight while carrying her her first child, daughter Maxwell, born in May 2012. She took a break from the program to have son Ace, who arrived in June 2013, but then got back on the WW bandwagon with ads billing herself as a work in progress.
That progress has resulted in weight loss estimated at 60 to 70 pounds. On social media back in March, she announced that she'd reached her goal weight.
"I didn't gain as much weight in my second pregnancy, but I still gained a lot of weight," Simpson told ABC News in October. "Any woman, dealing with their body after pregnancy, you look at yourself and you're like, 'What just happened to me?'"
She said she didn't diet during either pregnancy, but did eat a bit more sensibly when carrying Ace.