Obesity is a serious problem in the United States. According to the US Centers for Disease Control and Prevention, more than one-third of American adults are currently obese.

Led by Gregory Steinberg of McMaster University's Michael G. DeGroote School of Medicine, a team of researchers published a study on a certain hormone that could be linked to obesity, and that hormone just happens to be serotonin.
 
According to the study published in Natural Medicine, there are 2 types of serotonin. The type that is known for its effects on mood and appetite only accounts for 5% of serotonin in the body, while the other 95%, called peripheral serotonin, plays a role in obesity. Apparently, too much peripheral serotonin in the blood inhibits the brown fat that burns energy and glucose to make heat, which leads to obesity and the development of diabetes.

A previous study showed that preventing the formation of peripheral serotonin results in more active brown fat. In this more recent study, tryptophan hydroxylase (Tph1)—the enzyme responsible for the production of serotonin—was blocked or removed in mice that were fed a high-fat diet. This resulted in the improved ability of brown fat to burn more calories, thus protecting the mice from obesity and its complications.

Study co-author Waliul Khan stated that the high-fat diet prevalent in the United States is “an environmental cue that could be causing higher serotonin levels in our body.” In addition, Steinberg noted that preventing the production of peripheral serotonin will not affect serotonin in the brain, unlike earlier weight-loss drugs that curb appetite yet alter such serotonin levels, leading to an increased risk of depression and suicidality.

The same group of researchers are currently working on developing an “enzyme blocker” medication that will inhibit Tph1, thereby decreasing the amount of serotonin in the blood and combating obesity.