Depression is believed to increase the risk of heart disease, and studies suggest that the accumulation of visceral fat may be one of the reasons. This type of fat, also known as belly fat, collects around the internal organs at the waistline and is known to increase the risk of heart disease and diabetes.
As part of a larger study on middle-aged women, researchers screened 409 women for depressive symptoms. They also used CT scans to measure visceral fat and subcutaneous fat, which is found just below the skin. Waist size or waist-to-hip ratio is often used to estimate a person's amount of visceral fat, but the researchers point out that this type of measurement is inaccurate since it includes subcutaneous fat.
After adjusting for other risk factors, the researchers found that each one-point increase on the depression scale was associated with more than one extra square centimeter of visceral fat. Participants with scores that indicated clinically significant depression had 25 percent more visceral fat than women without depression.
The researchers say that more studies are needed to determine why depression may increase visceral fat, but they suspect that depression may increase the production of a stress hormone and inflammatory compounds that may lead to fat accumulation.
In addition, researchers analyzed data from the Coronary Artery Risk Development in Young Adults Study (CARDIA), a 20-year study in which more than 5,100 men and women participated. Investigators of that study had weighed and measured the waist circumference and body mass index (BMI) of participants and also asked them to rate their level of depression every five years.
Over a 15-year period, all the participants gained some weight, but those who were depressed at the beginning of the study gained it faster. By the end of this study, the waist circumference of subjects who reported a high level of depression was (on average) an inch larger than those with lower levels of depression. However, being overweight at the start of the study did not influence the development of depressive symptoms over time.
These findings support evidence that links cortisol, the so-called stress hormone, with both depression and abdominal fat. People who are depressed may have higher levels of belly fat due to elevated levels of cortisol.
Sources: Psychosomatic Medicine, Volume 71, page 410, May 2009; American Journal of Public Health, Volume 100, page 1040, June 2010