Most cats can't get the ball out very easily.

There have been others that have come on here wanting to get their cats to lose weight but not wanting to take their cats to the vet... If a cat is significantly overweight suddenly cutting back food and calories is very dangerous. So the warning had to go on there.

That sadly, would not work for any of my cats. They would destroy it the second I turned my back. With the exception of two of them, they're all brats that way.

(note: it could be empty, never held any food, and a couple of them would still feel the need to tear it apart)
If it works for you, good. Still make sure you're measuring. Just doing that helps a lot. Also, wet food is better for getting cats at a healthy weight and to stay there.