More than once, I have had a female client come in to work with us directly after a doctor did a bone density test and said they were at high or medium risk for osteoporosis. On our program, they started lifting weights, and only one year later had their bone density retested and the bone loss was reversed -- they went from being at high risk for osteoporosis to low risk with only a year of effective strength training. I have seen the actual DEXA scans of my clients with my own eyes in the real world and see that absolutely, without a doubt, strength training will increase bone mass and reduce, even reverse, your risk of osteoporosis.
I have always said that there are far more benefits to strength training for women than there are for men, including a decreased risk of osteoporosis. In an article on MSNBC by Amanda Chan, she stated that women are twice as likely as men to break a bone due to osteoporosis. This is why it is twice as important for women to lift weights.
Bone mass usually decreases as we age. Lifting weights can actually help you to increase it. This is also something to keep in mind when you are focused on that number on the scale -- your bone weighs something, and as you are getting stronger so are your bones, which will add weight to the scale. Just remember to keep in mind that this is a good thing! There have been numerous studies which have shown weight bearing exercise increases bone mass. One in particular was a one-year study where they used a strength training routine three days a week and showed in women, the more weight they lifted the greater the increase in total body bone mass density. Another study done in 2007 had young women participate for five months in a resistance training program, and the conclusion was that strength training increased bone mass. A third study was done in 2000 that showed that the positive effects of resistance training on the musculoskeletal system reverse when training is withdrawn. If you don't use it you lose it!
The scary thing is that some women have gone to extremes to lose fat and have followed drastically low-calorie and therefore low-nutrient diets, including cleanses and other extreme measures along with over-exercising. These approaches may have actually caused more damage to their bodies, possibly even putting themselves into increased risk for osteopenia or osteoporosis.
To reduce your risk of these diseases, use a strength-training program that challenges your system and puts a demand beyond what it is used to along with fueling your body with nutritious fuel. Your body is probably not going to respond to an exercise program that includes lifting weights that weigh less than your purse. Keep in mind that your body is already used to carrying your purse everyday. The average women's purse is probably 10 pounds. This means that to create a demand on your muscles and bones you should consider lifting weights that are challenging but that you are able to still keep proper form with. If you are not eating enough to fuel your body to do a challenging workout you will not benefit.
References:
Cussler, Lohman et al. 2003. Weight lifted in strength training predicts bone change in postmenopausal women. Med Sci Sports Exerc. 35(1):10-7
Nickols-Richardson, S.M., Miller, L.E., Wootten, D.F., Ramp W.K. and Herbert, W.G. 2007. Concentric and Eccentric isokinetic resistance training similarly increases muscular strength, fat free tissue mass and specific bone mineral measurements in young women. Osteoporosis Int. 18(6):789-96.
Winters, K.M. and Snow, C.M. 2000. Detraining reverses positive effects of exercise on the musculoskeletal system in premenopausal women. J Bone Miner Res. (12):2495-503.