Kourtney Kardashian flaunts her flat abs on an Instagram selfie this week.

The "Keeping Up With The Kardashians" star showed off her hard-earned washboard abs and tiny waist in an Instagram selfie she posted this week.

The reality star reportedly lost 45 pounds through exercise and diet. Kourtney follows low-carb organic diet programs Atkins and Paleo. She also works out regularly through yoga to keep her in shape.

At 36, Kourtney has three children. She gave birth to her third one in December 2015 and has considerably lost weight since then. Apart from diet and exercise, she drinks Fit Tea herbal weight loss tea, which she claims suppresses her appetite and enhances fat burning while detoxifying the body.

"I've been working out with a trainer, and having somebody else to work out with really helps motivate me," she said. "Some days Khloe will join me. I also try to eat really clean and at home as much as I can."

Kourtney shared on a blog post that she uses exercise to not only lose weight, but to cope with her anxiety brought upon by her breakup with Scott Disick July last year. The two split after nine years together. They have three children together: Mason, 5; Penelope, 3; and Reign, 10 months.

"Everyone deals with hard times in their lives differently. I'm generally not a nervous person but I get anxious. I also get nauseated; I feel like I can't eat when it is really bad, but I force myself to stay healthy," she wrote. "Still, when my anxiety is extreme, it feels like my body is constantly burning calories all day long. On these kind of days, I try to avoid caffeine, alcohol and too much sugar-basically anything that could make it worse."

As for her tiny waist, she and her sisters credit waist training for their fat bellies.

"I am pretty much the queen of multitasking," Kourtney wrote on an Instagram post with a snap of her wearing a blue waist cincher. "Obsessed with anything where I am doing more than one thing at a time, especially since I skipped the gym today. A little Saturday morning waist cinching and working on my posture while cleaning out my closet."

Her sister Khloe Kardashian also took similar waist training selfies as well as Kim Kardashian-West. Celebs that are also into waist training include Lindsay Lohan, Amber Rose and Kim Zolciak-Biermann.