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Weight loss influences bone parameters in older adults
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Older adults experiencing long-term or recent weight loss of at least 5% showed deterioration in both cortical and trabecular bone density and microarchitecture, especially at the weight-bearing skeleton, according to findings published in the Journal of Bone and Mineral Research.
“Weight loss is highly common in older adults; thus, patients and providers should be aware of the potential negative effects of weight loss on the skeleton,” Ching-Ti Liu, PhD, associate professor of biostatistics at Boston University School of Public Health, told Endocrine Today. “The magnitude of changes to the skeleton observed in this study translated into an almost threefold increase in the risk of fracture for those who lost 5% or more weight over 40 years.”
Liu and colleagues analyzed data from 1,361 older adults from the Framingham Offspring Cohort, which included the adult children and spouses of the original participants of the Framingham Heart Study (767 women; mean age, 70 years; mean weight, 79 kg; 19% with diabetes). Participants attended clinic visits that included physical exams, weight measurements and interviews every 4 to 6 years; the current study included participants who also underwent high-resolution peripheral quantitative CT (HR-pQCT) scans at the tibia and radius between 2012 and 2016 (researchers considered the clinical visit between 2011 and 2014 as the index exam). Researchers calculated long-term weight change from the baseline exam (between 1971 and 1974) to the index exam and short-term weight change from the clinic visit between 2005 and 2008 to the index exam. Researchers also assessed volumetric bone density and bone microarchitecture indices assessed via HR-pQCT and used general linear models to evaluate the association between bone parameters and long-term and recent weight change.
The mean relative long-term weight change was 9%, and mean relative recent weight change was –1%. Within the cohort, 12% (n = 166) had long-term weight loss of at least 5%, and 22% (n = 301) had recent weight loss of at least 5%.
Researchers found that both long-term and recent weight loss were associated with lower cortical density and thickness, higher cortical porosity and lower trabecular density and number. Results persisted after adjustment for age, sex, height, current smoking status and diabetes status; however, there were stronger associations observed at the tibia vs. the radius after adjustment, according to researchers.
Additionally, researchers also noted that trabecular volumetric bone mineral density and failure load were lower in people with long-term weight loss; however, this was not observed in adults with short-term weight loss.
“An interesting finding, however, was that the lower values for many of the microarchitecture measures that were observed in the weight-loss group were accompanied by an increase in the total area of the bone,” the researchers wrote. “This suggests the possibility that as loading of the skeleton is reduced with weight loss, the reduction in bone density and cortical thickness may lead to a compensatory expansion of the periosteal surface to maintain bone strength.”
Sensitivity analyses that adjusted for baseline weight, covariates assessed at baseline vs. the index exam and variability in weight over time in the analyses of long-term weight change did not change the findings, according to researchers. In sex-specific analyses, however, the observed associations were stronger in women vs. men.
“This study expands our understanding of the effect of weight change beyond DXA areal BMD to state-of-the-art HR-pQCT measures of trabecular and cortical volumetric BMD and microarchitecture,” Liu said. “Further work is needed to evaluate if the deficits identified in this work can be prevented through interventions or therapy.” – by Regina Schaffer
For more information:
Ching-Ti Liu, PhD, can be reached at Boston University School of Public Health, Department of Biostatistics, 715 Albany St., Boston, MA 02118; email: ctliu@bu.edu.
Disclosures: One study author reports she has received an institutional grant from Dairy Management Inc. and serves as a member of the National Dairy Council’s Nutrition Research Scientific Advisory Committee. Another author reports he has received grant support from Dairy Management Inc. and royalties for publication of books from Wolters Kluwer and Springer.
Perspective
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In this study the researchers looked at bone quality, which hasn’t been examined previously with respect to recent and long-term weight loss. The results are important since this is a large cohort and shows longitudinal results. It is interesting that weight loss negatively affected the tibia more than the radius, suggesting that weight bearing, and not a change in hormones due to caloric restriction, is the mechanism causing harm to bone. Hence, increased exercise during dieting may attenuate the negative effects. Also, because adults with obesity have compromised cortical bone density and thickness, these results are of special concern.
In intervention trials looking at calcium absorption that my colleagues and I have conducted, we found that caloric restriction decreased calcium absorption. That would be one mechanism that can put a person who is dieting at risk for bone loss. Calcium balance is important. During dieting, it is imperative that a person get the recommended intake of calcium to maintain calcium balance, preferably 1,000 mg to 1,200 mg, depending a person’s age and sex. Findings from the Women’s Health Initiative study led to the conclusion that high calcium intake could be harmful. Indeed, more than 2000 mg/day is the upper level of calcium intake recommended by the Institute of Medicine, and this can lead to kidney stones. However, no one should be frightened by the current recommended intake of calcium. That’s one way to offset the bone loss that can result from weight loss. Because this study emphasizes that weight loss compromises bone quality that can increase fracture risk, it is prudent to take adequate amounts of calcium, vitamin D and protein and to exercise during dieting to help attenuate loss of bone density and quality, particularly for older individuals.
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