Christine Weight change was my mother's concern, while a waist belt is resistant to it.
Resistant to it in that the security is less compromised by reducing one's body weight?
I only have experience with my hip style belt, but that does seem likely. If I were an unwilling wearer, I'd drop weight until I could fit my hand down the front. I would look waifish, but I think it would work. I suspect this bypass would be much harder with a waist style belt because the shape of my waist changes much less than my hip area when I am very thin.