Cortisone is a synthetic drug that metabolizes in the body to form the hormone cortisol. As if 2011, the exact relationship between cortisone and weight gain was uncertain. Cortisol naturally produced in the body has no proven effect on weight gain, despite some claims to the contrary. Weight gain is sometimes reported as a side effect of cortisone injections, however.
Cortisol is produced in the adrenal cortex, which is the outer portion of the adrenal gland. Women have elevated levels of cortisol during some portions of pregnancy. It is nearly always present in the body in some amount, but its production is increased by stress. This has led it to be nicknamed the "stress hormone."
Many studies have indicated that people tend to gain weight when they are stressed. Some researchers proposed a tenuous connection between cortisol or cortisone and weight gain. There are many factors, however, that connect stress with weight gain, including behavioral changes, such as reduced sleep and exercise and increased caloric consumption. Correlation does not necessarily imply causation, however. Although increased cortisone and weight gain may be found together, it does not follow that cortisone is the primary cause of the weight gain.
In the early 21st century, there was a surge of products that claimed to cause weight loss by blocking natural cortisol production. The US Federal Trade Commission ruled in 2007 that these claims did not have sufficient evidence to back them up. Companies that had marketed these products were forced to repay their customers.
Synthetic cortisone injections are sometimes given to reduce swelling in joints as a result of rheumatoid arthritis. Over a long period of time, some patients notice a connection between cortisone and weight gain. The exact reason for this is unknown. Not all patients experience weight gain as a side effect of cortisone injections regardless of how long they take the treatment.