In Australians with European roots, having more vitamin D in your blood might help you burn more calories while at rest—but if your body is better at using insulin, that calorie-burning boost might not be as strong.

In people of European descent living in Australia, having more or less vitamin D doesn’t seem to change how many calories your body burns at rest — any small effect vitamin D might have is probably canceled out by how it affects your body’s insulin response.

In people of European descent living in Australia, how much energy their body uses at rest might be linked to their vitamin D levels—but only if you use certain ways to measure insulin sensitivity. Some methods show a clear link, others don’t, so not all those methods are equally good for this kind of study.

If you have more vitamin D in your body, your body burns more calories while you're just sitting still—even if you don’t move more or eat differently.

In people who are overweight or obese, having more vitamin D in their body seems to be linked to how many calories they burn at rest, and this link happens because of how their body uses the vitamin D receptor gene — but not because of the PGC-1α gene.

In Australians with European roots, people whose bodies use insulin more efficiently tend to burn fewer calories while at rest — like their bodies are on a lower energy setting when they're not moving.