Kate Middleton has been known to be very active and sporty even before officially becoming the Duchess of Cambridge. But, despite having three kids now and a hectic work schedule as a working mom and royal, she seemed to have maintained her fit and slim physique throughout the years.

Earlier this week, Kate Middleton attended an engagement where she met the Olympian, Jessica Ennis-Hill, and Taekwondo professional athlete, Lutalo Muhammad. As per Express UK, the event in London for SportsAid saw the "sporty side" of the Duchess of Cambridge as she participated in various activities like sprint and Taekwondo.

The publication reported that fans and followers of the royal were quick to notice how she has maintained an "enviable" and impressive figure. As it happened, she did these activities together with the experts and professionals in the field.

Most of the royal fans shared their thoughts on various social media platforms and stated that Kate Middleton should write a book on how to stay slim. Some even went on to state that it is "good" to see her sporty side again.

As per Harper's Bazaar, the Duchess has never revealed her secrets directly. Even so, several royal insiders and sources reportedly shared hints and ideas on how she has been able to stay fit and healthy.

It was claimed that she and her sister, Pippa Middleton, are true "sports junkie." Amid all the busy schedules, they still spend an hour or two every day to exercise and get active.

Some sources claimed that Kate Middleton always loves to include "planks" to her daily exercise routines. Whatever the variations, though, she was said never to skip planking.

Other reports also added that the Duchess of Cambridge and the Duchess of Sussex share the same interest and love for yoga. If Kate is not doing a "rigorous" exercise for the day, she will reportedly choose to do a quick yoga routine, especially on days when she is stressed.

Sports is also another factor why Kate Middleton has maintained a very fit figure. It was revealed that she always enjoys a "make-up-free aqua aerobics" with Pippa and water polo with her husband.

Aside from her fitness routines, her diet also plays a huge role in her current figure and weight. As stated by the sources, the Duchess of Cambridge always prefers to consume home-grown raw foods and ingredients.

The Dukan Diet is also one of her tricks to staying slim. This diet was noted to focus more on protein and low-carb foods.