If they are really uneasy about doing any kind of measurements or weight right now, I wouldn’t worry about that right now. I’ve found that It’s perfectly understandable for some people who might have issues with the way they look or feel at this point. Try to slowly start into a program and keep really good records of total rep, hr, and times for now. This way you can show them that they have been improving as you see these things improve, but I wouldn’t push it on them. As you build rapport with the client they should come to trust you a little more and they will listen to why these things are quite important. I found really trying to build that initial relationship through trust is very vital before moving forward with a client.
I would just really try to remember you are there to help them get what they want, not what you want. So I have found trying to push somebody before they feel ready never really helped the situation.