ESPE Abstracts

The mineralisation measured by DXA, bone-mineral-content (BMC), of obese boys seems to be better than that of lean boys and It is known that obese children are taller than healthy children. Is this the only factor that explains the better DXA measurements of obese boys? And how explain the fact that these boys have more fractures of the extremities? We described bone mineralization in boys with overweight/obesity and leanness in relation to body composition. Cross-sectional study in Angers University Hospital with 249 overweight/obese boys aged 8-18 who underwent DXA. Bone mineralization was compared with data from 301 lean boys of similar age and height from NHANES 2011-2015, using the same DXA model. Whereas height was comparable in obese and lean boys, TBLH-BMC values were higher in obese compared to lean boys: the mean adjusted difference between obese and lean boys for TBLH-BMC, TBLH-BMC-Z-score, and TBLH-BMC-HAZ-score was 241 ± 20 g/cm2, 1.14 ± 0.07 Z-score, and 1.16 ± 0.08 HAZ-score (P < .001 for all comparisons). We also examined the relationship between bone mineralization, lean body mass index, and fat mass index : Each 1 kg/m2 increase in BMI was associated with an increase of +39 ± 6 g of TBLH-BMC in lean subjects vs +25 ± 3 g of TBLH-BMC in obese subjects (P < .05): the effect of a similar mechanical load (an increase of 1 kg/m2 in BMI) on bone mineralization was approximately 40% lower in obese compared to lean boys. More specifically, each 1 kg/m2 increase in lean body mass index had a similar positive effect in lean and obese boys (+78 ± 5 g of TBLH-BMC, not different). In contrast, the fat mass index had a significant negative effect: each 1 kg/m2 increase in FMI was associated with a decrease of 9 ± 3 g of TBLH-BMC. We observed that the TBLH-BMC and lumbar BMD were higher in obese compared to lean boys, even after accounting for height. These findings suggest that these higher values may be due to the increased mechanical load associated with increased weight. However, the positive relationship between body mass index and TBLH-BMC by multiple regression analyses was less steep in obese boys than in lean boys. The increase in bone mineralization in obese children does not adapt to the increase in body mass. Lean body mass, however, had a similar positive relationship with bone mineralization in obese and lean boys, whereas fat mass had a negative impact.