Bariatric surgery is an effective weight loss strategy for the obese population and ameliorates numerous metabolic problem. Bone loss accompanies weight loss and there is paucity of bone loss data in bariatric surgery particularly in Asian subjects. DXA (Dual X-ray absorptiometry) is the gold standard for bone density measurement however obesity and rapid weight changes can affect its accuracy. QCT is less affected by these changes. We examined 21 Asian subjects before and 1 year after bariatric surgery using DXA and central QCT (Quantitative computed tomography) to assess bone loss.
21 Obese Asian subjects, median BMI 39.7 kg/m2, underwent bariatric surgery (sleeve gastrectomy n=10, gastric bypass n=11). Baseline and 12 month post-bariatric surgery clinical measurements, laboratory and radiology were performed (including DXA and QCT of the spine and hip). Nutritional optimisation (including vitamin D supplementation) was done according to local practices. Univariate analysis using Fischer's exact test was employed with SPSS 21.
Median weight loss was 26 kg (p<0.05) or 24.2% of baseline weight, and median BMI dropped to 29.7 kg/m2 (p<0.05). Bone loss at the spine was not significant by DXA (p=0.96), however it showed a 10.9% drop by QCT (p<0.05). At the hip, QCT showed that the cortical component was unaffected by bone loss and the trabecular component showed a drop of 3.3% (p<0.05). Median vitamin D levels rose from 23.7 mcg/L to 29.9 mcg/L with vitamin D supplementation (p<0.05), and only 2 patients were still vitamin D insufficient 1 year post bariatric surgery.
Bone loss accompanied effective weight loss in bariatric surgery in Asian subjects that was better captured on QCT than DXA at the spine. Trabecular bone loss was predominant in this studied population. Further studies would be needed to assess effective means of ameliorating bone loss post-bariatric surgery.