Spotlight on Research for 2007

October 2007 (historical)

Scientists Examine Peak Bone Mass Timing and Body Fat Related to Bone

Osteoporosis has been called "a pediatric disease with geriatric consequences," because the bone mass attained in youth is an important determinant of lifelong bone health.

Two recent studies funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) are shedding light on the development of bone mass in children and adolescents. Focusing on two important issues in bone biology, the research suggests that bone mass may actually peak earlier than is currently believed, and that body fat does not contribute to bone strength.

There is much controversy concerning the timing of peak bone mass, the point at which bones have reached their maximum strength and density. Earlier studies using dual energy x-ray absorptiometry (DXA) have suggested that bone mass peaks long past sexual and skeletal maturity, potentially into an individual's late twenties or beyond. However, investigators at Children's Hospital Los Angeles are challenging this concept. Tishya Wren, Ph.D., and her colleagues used both DXA and computed tomography (CT) to measure the bone mineral densities of 50 females 14 to 20 years of age. Measurements were taken at baseline and 3 years thereafter. It is the combined use of these two bone assessment technologies — DXA and CT — that enabled the major insights into the relationships among the lean body mass (muscle), fat, and bone mass.

Wren and her team discovered that CT values for bone mineral density peaked around the time of sexual maturity and the cessation of longitudinal growth, while DXA values continued to increase beyond sexual and skeletal maturity. The authors suggest that the longer period of bone acquisition suggested by DXA are likely due to soft tissue changes - such as increases in muscle and fat - but are not true increases in bone mass. "This discovery should help define the narrow window of time during which interventions to enhance the peak bone mass are likely to be most effective," says Wren. "Optimizing peak bone mass is an important strategy for preventing future osteoporosis."

In a separate study, a second team of Children's Hospital Los Angeles researchers challenged a widely held belief that body fat enhances bone strength. Vicente Gilsanz, M.D., Ph.D., and his colleagues recruited 300 healthy white teenagers and young adults between the ages of 13 and 21 years of age. Half were female and half were male. Bone density (using DXA and CT) and fat and lean body mass were measured in each participant.

Consistent with previous studies, investigators found a strong association between lean body mass and bone strength. However, fat body mass had either no effect or a negative effect on bone. According to Gilsanz, "The common belief has been that fat mass is beneficial to the skeleton and enhances bone formation. This positive fat-bone relation was primarily based on studies using DXA measurements of these two tissues, and did not account for the confounding effect of fat on bone measures. In contrast,we used CT, which is not influenced by fat, to assess bone, and found that fat is not beneficial and could even be harmful to the young skeleton ."

# # #

The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the Department of Health and Human Services' National Institutes of Health, is to support research into the causes, treatment and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about NIAMS, call the information clearinghouse at (301) 495- 4484 or (877) 22-NIAMS (free call) or visit the NIAMS Web site at . Information on osteoporosis and other bone disorders is available from the NIH Osteoporosis and Related Bone Diseases~National Resource Center; phone toll-free 800-624-BONE (2663), or visit .

Wren TA, Timing of peak bone mass: discrepancies between CT and DXA. J Clin Endocrinol Metab. 2007;92(3): 938-41.

Janicka A, Fat mass is not beneficial to bone in adolescents and young adults. J Clin Endocrinol Metab. 2007;92(3):143-7.