A randomized controlled trial looked at the dose-response relationship of vitamin D supplementation in obese participants after two months and found that it was significantly lower than healthy participants. In other words, obese participants required more vitamin D to reach similar levels as healthy participants.
The dose-response relationship describes the change in effect in an organism caused by differing levels of doses of substances after a certain amount of time. In this study, the researchers were looking at how a certain dose of supplemental vitamin D affected the serum vitamin D levels in obese individuals after two months.
Obesity is considered a risk factor for vitamin D deficiency. Obese individuals have consistently been found to have lower vitamin D levels and a greater likelihood of deficiency than non-obese individuals.