Obesity and depression often go hand in hand. But does being obese make people depressed, or can depression cause weight gain?
In a society enamoured with thinness, many assume that being fat is depressing, and that if there is a cause and effect relationship, it's obesity that makes people feel down. But “there is an alternative explanation”, says Belinda L. Needham, an assistant professor of sociology at the University of Alabama, Birmingham. “And, that is that being depressed actually makes you gain weight.”
Her new study found that young people who reported symptoms of depression such as feeling sad or hopeless gained weight more rapidly over a 15-year period and accrued more belly fat than those who appeared to be happier. In the study, it was found that those who were obese initially may have been depressed, but did not become more depressed over time.
“When you're depressed, you tend to be inactive and not to exercise as much, and you tend to eat more,” Dr. Needham says. “And, if you experience high levels of depression and take anti-depressants, those drugs are associated with weight gain as well.”
She noted that there could be some third underlying factor that is actually causing both the depression and the obesity. “We think that chronic stress is the mediator and that chronic stress arousal leads to ‘depressed affect', which then leads to excess weight gain,” she says.
The stress hormone cortisol, for example, stimulates and promotes fat storage, especially in the abdominal area, since the body has evolved to store calories during times of stress.
Stigma-related depression
The relationship between obesity and depression has always been a murky one. Some obesity experts, such as Yale University's Kelly Brownell, say that the “causal arrow goes both ways”, but that the stigma surrounding obesity leads to discrimination and unrelenting bias that inevitably results in depression.
Dr. Needham notes that public health efforts to rein in obesity that don't take emotional well-being into account and treat underlying depression may fall short. “Obesity and depression are both really serious public health issues that everyone is concerned about, but we don't really understand a lot about the relationship between the two,” she says.
“We tend to separate the mind and the body in our culture, but they're much more connected than we realise,” she adds. “We're not going to understand how to treat obesity if all we focus on is diet and exercise.”
Her study analysed data from 5,115 men and women ages 18 to 30 who participated in the Coronary Artery Risk Develop in Young Adults, or Cardia, study. Participants took a survey to assess symptoms of depression every five years, and their body mass index and waist circumference were tracked over time.
The researchers found that while everyone gained weight over a 15-year period, those who had a high body mass index did not become more depressed over time. Those who reported more symptoms of depression, however, put on more abdominal fat over time: they started with a waist circumference that was about 1.6 cm, or about six-tenths of an inch, greater than those with few depressive symptoms; by year 20, their overall waist measurements were 2.6 cm, or over an inch, bigger than the group that was not depressed.
Earlier studies have come to mixed conclusions. A study of teenagers in middle school and high school found, as in Dr. Needham's study, that being depressed predicted obesity a year later, but that being overweight was not associated with a subsequent increase in depression. A study of older adults, however, found the opposite: that obesity at the start of the study was associated with an increased risk for depression five years later, but that initial depression was not linked to a greater risk for obesity later.
Those discrepancies between the young and old may have something to do with age and developmental differences, says Bruce Blaine, a health psychologist at St. John Fisher College in Rochester, who reviewed 16 studies on the link between depression and weight gain and found depressed people were at significantly higher risk for becoming obese.
Most dramatically affected were teenage girls, who were two-and-a-half times more likely to become obese if they were depressed. “Depressed people are not that different physiologically from stressed people,” Dr. Blaine says. “Their sympathetic nervous system is chronically turned on, and one of the consequences of this is increased fat storage.
“We tend to think of depression as an outcome that something else causes us to become depressed. We don't think of depression as a cause of other health outcomes,” he adds.
