Discussion
obesity, fracture, weight loss, bone loss
OSTEOPOROTIC FRACTURES, OBESITY, SECONDARY, BONE LOSS
In the Look AHEAD clinical trial in persons with overweight and obesity and with DM, we previously found that an intensive lifestyle intervention that resulted in intentional long term weight loss and improved fitness increased the risk of frailty fracture [Our finding of increased bone loss with weight loss is consistent with other reports from the Osteoporotic Fractures in Men Study which found that weight loss regardless of intentionality is associated with an increase in bone loss [We did not observe any differences in bone density changes at the lumbar spine, comparing the two treatment groups. Interestingly, men in both groups experienced increased BMD of the lumbar spine a finding that is consistent with reports from other studies of increasing spine BMD as measured by DXA with aging [The total number of bariatric surgeries in the DXA subgroup was very small and thus we were not able to examine this surgical procedure’s effect on bone by treatment assignment in the current paper. Although beyond the scope of this paper, it is worth noting that bariatric surgery is an increasingly utilized weight loss strategy in this population [The strengths of the Look AHEAD clinical trial include randomization to group assignment, high levels of retention during longitudinal follow-up, a racially and geographically diverse participant population, and successfully producing long-term intentional weight loss and improvements in physical activity and fitness. Further, the DXA measurement in the DXA substudy and fracture ascertainment in the whole Look AHEAD group were preplanned secondary outcomes of the trial. The DXA data was also rigorously monitored by the DXA quality assurance center and longitudinal performance was assessed with regular scanning of spine and whole body phantoms on each densitometer.There are several considerations to put interpretation of our findings in context. Look AHEAD did not collect information regarding calcium and vitamin D intake in the DXA subgroup, thus we are unable to examine the observed bone changes in relation to these variables that are known to be important for bone health in both men and women [Another limitation of the substudy is use of a DXA scanner in the setting of weight change. With obesity, the long-term precision of the DXA scanner is reduced which may result in attenuation of associations between changes in weight and BMD [