The exercises in this video are effective at increasing your range of motion and work the core muscles but they aren’t overly difficult. All of these movements work much more than just your abdominals; your entire core (abs, obliques, lower back), and butt, thighs, and upper body all have to work to get these moves done.
Because these things take time to produce a visible change in your body composition, consistency is also very important. You can’t do three days of brutal workouts on a near-starvation diet and expect to get good (or healthy) results. Make small, sustainable habits to your routine and you will develop hard-earned results that are much healthier and much easier to maintain.