Obesity and depression: Investigating the link

 

• There is a two-way relationship between obesity and mental health conditions, including depression and anxiety.
• A study in mice suggests that eating a high fat diet may disrupt a newly discovered neural circuit in the brain that governs both mood and appetite.
• A combination of two drugs that act on this circuit not only reduced signs of anxiety in the animals but also led to weight loss.
• The animals lost weight after the treatment not only because they ate less but also because they preferred more healthy foods.

By 2030, experts predict that nearly half of all adults in the United States will have obesity.

There are well-known links between obesity and a wide range of physical illnesses, including type 2 diabetesTrusted Source, hypertensionTrusted Source, rheumatoid arthritisTrusted Source, and some forms of cancerTrusted Source.

However, there is also a complex two-way relationship between obesity and mental illness.

According to a report from the Centers for Disease Control and Prevention (CDC), 43%Trusted Source of the U.S. adults aged 20 years and over who are living with depression also have obesity. There is also an association between mental illness in general and obesity.

Weight gain is a recognized side effect of many antidepressant medications. Conversely, research suggests that obesity can have a psychological effect on people that predisposes them to depression.

But researchers believe that there may also be a more direct, physiological link between the two conditions.

Among the possible causes that obesity and mental illness may have in common are:

• inflammation
• hormonal disturbances
• genetic factors

Brain circuitry

There is also a possibility that certain neural circuits in the brain predispose people to both obesity and mental health conditions. However, exactly where these circuits are and how they work have been unclear.

Researchers from Baylor College of Medicine in Houston, TX, recently led a team of researchers that may have discovered such a circuit in mice.

The team found that feeding mice a high fat diet disrupted the circuit, which led not only to weight gain but also to signs of anxiety and depression on standard behavioral tests.

When the researchers used genetic techniques to restore the normal functioning of nerve receptors in the circuit, this resulted in weight loss and eliminated the animals’ signs of anxiety and depression.

Remarkably, despite still having a healthy appetite, the mice reduced their food intake and were no longer interested in high fat food.

“We were surprised to see that the animals lost weight not because they lost their appetite but because genetically aided readjustment of the mental states changed their feeding preference from high fat to low fat food,” says Dr. Guobin Xia, a postdoctoral associate at Baylor who is co-first author of the study.

Two drugs that target the same nerve receptors in this brain circuit had similar beneficial effects on the mice and their feeding preferences.

Source: Medical News Today