The study was conducted by researchers from Brandeis University. Previous studies have already established an association between psychological stress and the triggering of biological responses similar to the effects of illness or injury, including inflammation. While inflammation is a good thing, runaway inflammation increases the risk of chronic and life-threatening diseases.
"We've known that overweight and obese individuals already have chronic, low grade inflammation," says psychology professor Nicolas Rohleder, the study's principal investigator, in a press statement. "Now, it seems that when you add stress to the mix, it's a double hit."
For the study, the researchers measured interleukin-6 (IL-6), an inflammatory agent linked to stress, to evaluate inflammation levels in normal-weight and overweight individuals over the course of two psychological stress tests. They then divided people according to their weight based on several other factors like BMI and body fat percentage.
Researchers noted that lean and overweight individuals reacted the same way to stress on the first day of testing, despite higher starting levels of IL-6 in overweight participants. However, on the second day, researchers observed an elevation in the IL-6 levels of overweight participants, which nearly doubled.
"It seems that every percentage point of body fat makes your more susceptible to inflammation," says McInnis. "With about two thirds of Americans classified as overweight, and worldwide obesity rates doubling since 1980, understanding the health risks of obesity could not be more important. We know that there are serious diseases associated with obesity. Now we are one step closer to understanding how and why."
The findings were published online in the journal Brain, Behavior and Immunity.
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