The Keeping Up with the Kardashians star posted an image of her running in a basketball court while wearing workout gear with the caption "let's go," and "no equipment necessary."
Later, she posted an image of her meal, showing avocado, cheese, lean white meat, lettuce, and veggies with seeds and nuts on top.
"Keto starts today..." she captioned the image.
The 41-year-old mom also posted a link to her Poosh website that offered "keto hacks" to stay on track with fitness.
"I wanted to start summer feeling (and looking) my best, so I decided to go back on keto for the second time," she said.
While she admits that starting a new diet is exciting, sticking with it is the hard part.
"Staying with it is the hard part. It's not even about willpower as much as it is convenience. Running around with my kids, attending events and meetings, and keeping myself fueled for my busy schedule is the real challenge," she wrote.
Part of what makes her able to stick to the strict diet, which involves focusing on proteins and low-glycemic fruits and veggies, is taking the occasional day off to eat however she wants. On those days, she says she treats herself and doesn't feel guilty.
She also tests her blood every morning to make sure that she is in ketosis, a metabolic state in which the body produces ketones out of fat at a higher rate. Fans of the keto diet say that being in ketosis is important for weight loss, though there is some discussion in the health community about how healthy the state is.
Kourtney said that she has an avocado smoothie every morning for breakfast and travels with keto-friendly snacks like nuts. At night, she nibbles on one protein ball and tries not to eat late into the evening.
In mid-May, the 41-year-old admitted that she had been eating more than normal during the coronavirus pandemic lockdown. She said that she had downed four entire cakes over the past two weeks while talking to her sister Khloe Kardashian remotely.Kourtney said that she wasn't stressing about her weight gain, but that she was hoping to lose a few pounds. Kourtney has made a name for herself as a clean eater on the show, and her diet has sometimes been a focus of episodes. At one point, she and her sister Kim Kardashian got into a fight over having candy at one of their children's birthday parties.
Brother Rob Kardashian has also lost a few pounds in recent days, showing off his svelte new figure at Khloe's recent birthday party.