I would ask your rationale for this exercise. Most people do it to try to reduce “love handles”, but you cannot spot reduce. It is also not a very effective exercise as gravity is doing most of the work, even if you hold weights. It you are trying to strengthen the obliques I would suggest using a resistance band for this motion. You should also be aware that spinal flexion is not recommended for those with osteoporosis.
If you’re looking to reduce your sides, then no, this is a useless exercise. As Janet pointed out, you can’t spot reduce. Remember: you’re toning & building muscles with weights – not reducing their size. But even if you were looking to build those muscles, I would go with trunk rotational exercises vs. side bends.