Extreme body weights associated with either anorexia nervosa or obesity may affect areal bone mineral density (aBMD), bone remodeling, and levels of periostin in young women, according to study results published in The Journal of Endocrinology & Metabolism.
Previous studies have reported that weight has a significant effect on peak bone mass. In cases of extreme body weight, changes to bone metabolism may be secondary to variations in hormone and metabolic factors and mechanical constraints on the skeleton.
In the current study, researchers aimed to assess the effects of anorexia nervosa or obesity on aBMD, bone turnover, and periostin levels compared with healthy controls with normal weight. Furthermore, they analyzed these data by age and explored patient characteristics associated with aBMD.
The case-control study included 114 white women aged 16 to 27 years. The cohort comprised 38 women with anorexia nervosa and 38 with obesity (body mass index >95th percentile for age in those aged <18 years or >30 kg/m2 in those aged ≥18 years) recruited from the Montpellier University Hospital in France. The control group, recruited from the community by advertisement, included 38 healthy normal-weight aged-matched women.
Women with obesity had higher aBMD values at the hip (1.052±0.144 g/cm2 vs 0.934±0.111 g/cm2; P <.001), lumbar spine (1.056±0.107 g/cm2 vs 0.993±0.128 g/cm2; P =.006), and radius (0.588±0.046 g/cm2 vs 0.549±0.047 g/cm2; P <.001) compared with controls, respectively. Women with anorexia nervosa presented with lower aBMD values than controls at the hip (0.800±0.161 g/cm2 vs 0.934±0.111 g/cm2, respectively; P <.001), lumbar spine (0.877±0.138 g/cm2 vs 0.993±0.128 g/cm2, respectively; P <.001), and radius (0.525±0.046 g/cm2 vs 0.549±0.047 g/cm2, respectively; P =.003).
At the hip, aBMD was significantly higher in women with obesity compared with the control group or the anorexia nervosa group at age 19 years. After age 20 years, aBMD was lost with disease progression for women with anorexia nervosa, with significantly lower values compared with controls. At the lumbar spine, aBMD was higher in women with obesity and controls at age 20 to 22 years. For women with anorexia nervosa, the difference in aBMD at the lumbar spine vs other groups increased with age and became significant from 19 years onward.
Markers of bone formation (osteocalcin and procollagen type 1 N-terminal propeptide) were lower in patients with anorexia nervosa or obesity compared with the control group. Conversely, C-terminal telopeptide of type 1 collagen breakdown products, a marker of bone resorption, were only higher in women with anorexia nervosa compared with controls. Levels of periostin correlated with bone formation markers in the entire study population and were significantly lower in women with obesity compared with the control group and the anorexia nervosa group.
The researchers noted that while bone turnover markers were lower in older vs younger women in the control group, they remained relatively constant with age in women with either deficient or excessive body weight.
Of the factors studied, lean body mass had the strongest positive effect on whole-body aBMD in all 3 groups.
The researchers noted several limitations of the study, including its cross-sectional design and only a single measurement of aBMD and biologic parameters.
“[O]ur study demonstrated that weight conditions influence aBMD, the profile of bone remodeling, and the periostin levels. Moreover, the factors related to aBMD appear to be specific for each condition, but lean body mass was the parameter most consistently associated with aBMD,” concluded the researchers.
Maïmoun L, Garnero P, Mura T, et al. Specific effects of anorexia nervosa and obesity on bone mineral density and bone turnover in young women [published online December 10, 2019]. J Clin Endocrinol Metab. doi:10.1210/clinem/dgz259