People who lose weight through cutting calories alone may be losing bone density, and increasing their risk of osteoporosis while those who combine diet and exercis does not seem to produce the same effect, according to a report in the Archives of Internal Medicine, one of the JAMA/Archives journals.

Losing weight without proper exercise and a healthy diet can have disastrous effects on your body. Lack of exercise can result in decreased bone density, which increases the risk for osteoporosis (weakening of the bones) and hip fractures in older men and women.

Scientists, led by Dennis T. Villareal, M.D. from Washington University School of Medicine, St. Louis, and colleagues examined the effects of weight loss on bone loss in 48 adults (30 women and 18 men, with an average age of 57). Researchers divided the participants into three groups:

1. Restricted calories - 19 were assigned to follow a calorie-restricted diet (to decrease energy intake by 16 percent for three months, then by 20 percent for nine months).

2. Exercise - 19 were placed on a graduated regimen of exercise to increase energy expenditure by 16 percent for 3 months and then by 20 percent for 9 months, with no reduction in calories.

3. Information Only - 10 were simply offered information on healthy lifestyles only when requested.

All participants were weighed at the beginning of the study and again after one, three, six, nine and 12 months. Bone mineral density was measured every three months using a technique known as dual-energy x-ray absorptiometry. Blood tests were also taken at the start and at 6 and 12 months to see if bone tissue was being absorbed and regenerated.

After one year, the researchers found that those in the calorie restriction group lost an average of 8.2 kilograms (18.1 pounds) and lost bone density in three high-risk locations: the lower spine (2.2%), the hip (2.2%), and the top of the femur (2.1%), those in the exercise group lost 6.7 kilograms (14.8 pounds) with no significant loss of bone density and those in the healthy lifestyle group 3 showed no change in weight or bone density.

In both group calorie restriction and group exercise, people who lost weight also experienced increased "bone turnover," the process by which old bone is removed from the skeleton. while in the exercise group increased muscle action during exercise stimulated the creation of new bone material to compensate for that loss!

Take a note if you are trying to lose weight and protect your skeleton, especially if you are an older adult, mixing diet with exercise would be best for protecting your bones.