Weight training and osteoporosis

Hi all,
A friend of mine volunteered to be a normal control in a study on osteoporosis and had a bone scan performed, only to reveal a low bone mineral density in the spinal area!!
He was wondering how benifical weight training would be to him.
What type of trining should/could he do?
Does anybody have experience or knowledge in this area?

He is 24, does not play sport/train and is otherwise healthy. (Blood results).
I was thinking of basic circuit/body weight exercises.

Thoughts anyone?

A specialist will best advise but as well as checking nutrition issues and prescribing any necessary medication, will probably state jogging, light weights and circuits are very benefial and exercise is a necessity. Obviously the intensity depends on the severity of bone density, and in more severe cases, an improvement in bone density may be needed via medication/nutrition before exercise can begin.