How Weight Affects Bone Breaks: A Global Study

A recent worldwide study dug into how body mass index (BMI) affects the chances of breaking bones. Researchers looked at data from over 1. 6 million people across 32 countries, tracking them for about 16 million person-years. They found that being underweight increases the risk of hip fractures in both men and women. Interestingly, being overweight or obese seemed to lower this risk at first glance, but things changed when bone density was factored in. The study split people into different BMI groups: underweight, normal weight, overweight, and two levels of obesity. Initially, those who were overweight or obese had a lower risk of hip fractures compared to those with a normal BMI. However, when the team adjusted for bone mineral density (BMD), the picture shifted. The protective effect of being overweight or obese disappeared, and in the most obese group (Obese II), the risk of fractures actually increased, especially in men. For those who were underweight, the risk of fractures remained high even after adjusting for BMD. This suggests that low BMI is a strong risk factor for bone breaks, regardless of bone density. The study also found that the increased risk in the highest BMI categories was more significant in men than in women. These findings are important because they will help update a tool called FRAX, which is used to predict fracture risk. The study highlights the complex relationship between weight and bone health, showing that it's not as straightforward as more weight equals fewer breaks.