Research Strongly Links Obesity, Depression and Eating Disorders

Obesity is a cause of depression and is significantly associated with eating disorders, particularly in women. The findings are backed by two recent studies, one of which is suggested to have found the strongest evidence yet that the psychological impact of being overweight causes depression rather than diabetes and other associated illnesses.

The first study, “The effect of obesity on depression, eating attitude and nutritional status in adult individualsin the September 2018 issue of Clinical Nutrition, sought to identify the correlation between obesity, depression and eating disorders. Noting that the combination of obesity and depression are public health issues, researchers applied depression status and eating attitude scales to the daily food intake by 380 volunteer adults: 190 obese individuals with Body Mass Index (BMIs higher than 30 kg/m) and 190 healthy individuals (BMIs of 18.5-25 kg/m).

What they found was that the overall eating disorder rate was just under 10 percent, but was nearly 11 percent among obese men and 17.5 percent among obese women. Emotional eating attitude showed a significant increase in appetite and/or the consumption of food among the obese group—nearly 47 percent compared to just over 22 percent in the non-obese group—and depressive symptoms (17 percent overall) were higher among the obese participants (nearly 22 percent in general). The rate of depressive symptoms was also higher in the obese group, nearly 16 percent compared to nearly 9 percent in the non-obese group. Obese females experienced severe depressive symptoms more frequently, although there were no significant differences in energy and macronutrient intake by both groups.

“As a result, it was found that [a] significant association [existed] between depression and eating disorder[s], especially in the obese female individuals,” wrote the researchers, who further concluded that, “…an important approach for the prevention and the treatment of obesity is to examine the cause and effect relation between obesity and depression, eating disorder and nutritional status.”

In “Using genetics to understand the causal influence of higher BMI on depression,” published in the November 2018 issue of the International Journal of Epidemiology, researchers from the University of South Australia and University of Exeter in the United Kingdom (UK) found what has been called the strongest evidence yet that obesity causes depression, even in the absence of other health problems.

Researchers compared UK Biobank data from more than 48,000 people with depression to that of a control group of more than 290,000 people. Hospital data and self-reporting were used to determine whether people had depression. The psychological component of obesity was separated from the impact of obesity-related health problems using genes associated with higher BMI, but with lower risk of other conditions like diabetes.

Looking at individual-level data, researchers were able to further identify potential sex differences in the causal relationships between BMI and depression. The prevalence of depression is consistently higher in women than men. Further, women in the UK Biobank were 1.5 times more likely to report a diagnosis of depression.

“In summary,” researchers wrote, “using up to 340,000 participants from the UK Biobank, we provide evidence that higher BMI, as estimated by genetics, is causally related to higher odds of depression, especially in women.”

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