Some manufacturers ship CBD products nationally, an illegal action which the FDA did not enforce in 2018, with CBD remaining the subject of an FDA investigational new drug evaluation, and is not considered legal as a dietary supplement or food ingredient as of December 2018. Federal illegality has made it difficult historically to conduct research on CBD. CBD is openly sold in head shops and health food stores in some states where such sales have not been explicitly legalized.
A 2016 study in Molecular and Cellular Biochemistry explored how CBD contributed to the fat browning process. Brown fat is a particular type of fat that works to increase energy expenditure, and it produces heat. This allows brown fat to burn more calories, but adults are mostly composed of white fat. In the study, the following was observed as a result of cannabinoid usage: