We typically think of bones as inert, structural support, but scientists have discovered they may play a key role when it comes to regulating our appetite and helping us lose weight. New research published this year has identified a hormone released by bone cells that targets the parts of the brain that make us hungry.
In recent years, studies have shown that our bones release hormones affecting brain development, glucose management, kidney function and male fertility. Now this new study conducted on mice at Columbia University Medical Center has found that a new function of bone has been added to the list: appetite suppression.
Researchers found that bone cells secrete a hormone called lipocalin 2. Because of its chemical structure, lipocalin 2 had previously been identified as a protein that was secreted by fat cells. This hormone is released after eating and reaches peak levels approximately one hour after the meal has been consumed. The latest study showed that 90 percent of lipocalin 2 is actually produced by osteoblasts – bone cells that are responsible for building new bone.
The scientists wanted to know if bone-derived lipocalin 2 plays a role in regulating appetite, so they bred two types of mice: one type whose fat cells could not produce lipocalin 2, and one type whose bone cells couldn’t produce lipocalin 2. They compared the two groups to normal “wild type” mice.
The mice with the defective lipocalin 2 genes in bone were found to have 20 percent more body fat and ate 16 percent more food than mice whose fat cells couldn’t produce lipocalin 2. This group also had poor blood sugar control and insulin resistance. These results suggested that the bone-derived lipocalin 2 alone was responsible for the changes in appetite and metabolism.
When the mice with the broken gene were given lipocalin 2, their eating returned to normal. Injections of the hormone into healthy mice reduced the amount they ate and helped to regulate glucose and insulin levels. In all types of mice, lipocalin 2 suppressed appetite, improved overall metabolism, and reduced body weight. This effect was attributed to the lipocalin 2 affecting the parts of the brain that control hunger.
So what does that mean for us?
Luckily, lipocalin 2 is also released by human bone cells. Researchers tested levels of the hormone in a group of patients with type 2 diabetes who had elevated insulin and glucose levels and measured them against a healthy group. The results showed that those with higher levels of lipocalin 2 after eating had lower body weights and levels of blood sugar. It seems that the lipocalin 2 supresses the appetite similar to how a slimming pill might – but best of all, it occurs naturally in our bodies.
Scientists hope that in the future, this hormone could be used as a therapy for obesity and other metabolic disorders.
In the meantime, this is potentially good news for those who do any exercise that helps build bone density. After all, if we have larger bone mass it would theoretically increase the amount of lipocalin 2 we produce.
So what’s the best exercise for bone density?
Resistance training, such as BODYPUMP™, has been proven to increase bone density and high impact training places a stress on bone, which also results in an increase in bone density. The training involved in long distance running can also build bone density. This helps explain the low appetite often exhibited by long distance runners – which was highlighted in a 2016 study of a group of trained runners who ate significantly less after a 20km run when compared to a control group. What was interesting about this study was that the reduction in appetite was unexplained because it was not associated with a decrease the “hunger hormone” ghrelin – but perhaps this is an example of where lipocalin 2 was at play?
So, we’ve long known that high impact and resistance training is great for improving our cardiovascular fitness and promoting the growth of lean muscle tissue. Now we potentially have another benefit to add to the list: helping us to regulate our metabolism and lose weight.