Hi nurse kim..
I also work in the healthcare field, planned parenthood and a doctor who provides aboriton services.
Birth control can cause an increase in appetite for some women, you eat more, you gain weight..
Bc like nuva ring, yaz, and yasmin are known to cause fewer problems with weight gain.
An iud is non hormonal, and does not cause any hormonal side effects at all.
You may consider telling the ladies that eating healthy and staying healthy will ensure that they will not gain any 'unnecessary' weight on bc pills.