Serotonin acts as a neurotransmitter, a type of chemical that helps relay signals from one area of the brain to another. Although serotonin is manufactured in the brain, where it performs its primary functions, some 90% of our serotonin supply is found in the digestive tract and in blood platelets.
Which comes first? And how can you untangle the link between depression and weight -- especially if depression has sapped you of your energy to make changes? Here's what experts say you need to know.
Depression and Weight Gain
A March 2010 review of 15 studies, published in the Archives of General Psychiatry, linked obesity to a greater risk of developing depression - and vice versa.
But do people gain weight because they are depressed? Or do they become depressed because of the excess pounds they are carrying? No one knows.
“It’s a chicken and the egg phenomenon,” says psychologist Leslie Heinberg, PhD, who directs the Bariatric and Metabolic Institute at the Cleveland Clinic. “But we do know that depression has lots of symptoms that can worsen obesity - appetite disturbances, lack of energy, lack of motivation to do things.”
In 2009, researchers at the University of Alabama at Birmingham reported that depressed people tend to gain weight faster than people who aren't depressed.
Depression, of course, comes with its own set of risk factors, including suicide, social isolation, drug and alcohol addiction, and anxiety.
Whichever comes first - depression or overweight/obesity - it is a very unhealthy combination. Often, it is a self-reinforcing combo as well.
Eating Yourself Blue
“Some foods, especially foods with high sugar and/or fat content, make you feel better, if only briefly,” says psychiatrist James Gordon, MD, author of Unstuck: Your Guide to the Seven-Stage Journey out of Depression.
“That good feeling makes you want to eat more, which in turn makes you feel bad about yourself,” Gordon says. “That leads to deeper depression, and more eating, and greater amounts of weight gain. It’s a vicious cycle.”
Getting out of that cycle can be a real challenge.
“When you are depressed, it is much harder to get out of bed, much less pay attention to what you are eating,” says Edward Abramson, PhD, an emeritus professor of psychology at California State University at Chico and the author of Emotional Eating: What You Need To Know Before Starting Another Diet.
For doctors, it’s less important to know which came first: the patient's depression or the weight problems. The question is, which one should get the most initial attention?
“If someone comes to me who is severely depressed and overweight, the depression is going to be the primary focus,” says Abramson.
However, he continues, an eating disorder that causes a patient to binge might need to be addressed first: “If their eating is out of control, that becomes the primary focus.”