Can frequent strength training help prevent osteoporosis? how often, how much weight, what exercises?

Strength training : Yes. Preferably 2 to 3 times weekly and with an instructor (trainer) that can teach the proper form and technique. The weight amount is dependent on your strength. Also don't forget about impact sports such as walking, jogging , and running. All can help stress muscles to strengthen bones.

Most likely helpful: Strength training and other weight bearing exercises are proven and effective ways to increase bone density. Since osteoporosis is the result of weakened bones, strength training, especially to increase muscle mass at a younger age and maintained throughout the years are vital. Key values are 2-5 times per week, at 40-85% predicted max values lifted, and focus on whole body movements and exercises.