Individuals with obesity and type 2 diabetes or prediabetes have insulin resistance — which means that their bodies are unable to regulate blood sugar levels. But do these imbalances also mean that their emotional responses to negative stimuli are increased?
According to Auriel Willette, Tovah Wolf, and others at the University of Wisconsin-Madison and Iowa State University in Ames, the answer to this is "yes."
The scientists involved in the new study thought that this raised emotional response to stressors may have to do with insulin resistance, which sets up the context for an increased negative emotional response.
Their recent study — the results of which are now published in the journal Psychosomatic Medicine — indicates that individuals with type 2 diabetes or prediabetes react more strongly to negative visual stimuli.
This is backed up by their brain activity, levels of cortisol (the stress hormone), and their cognitive performance.
Insulin resistance tied to negative reactions
To gather data relevant for their research, the researchers recruited 331 adults using a larger study called Midlife in the United States.
The first sign that they studied in the participants was their "startle response," which is defined as an involuntary defensive reaction to a stimulus that is automatically perceived as potentially dangerous.
Imagine jumping, startled, because someone suddenly yells "boo!" from behind you in an otherwise quiet room. After a moment, you will realise that it was only a practical joke, but your body's instant reaction is to propel you out of harm's way.
However, some individuals have stronger, more intense startle responses than others, and it turns out that people with diabetes may fall into this category.
Willette and team showed each study participant a series of images with negative, positive, or neutral content, with the aim of triggering an emotional response.
At the same time, they tested the subjects' involuntary responses using an electroencephalogram (EEG), a test in which tiny electrical sensors are placed in key areas over the head and face — in this case, under the participants' eyes — to measure activity in the central nervous system.
In doing so, the researchers evaluated how often each individual blinked or flinched when shown negative imagery.
"People with higher levels of insulin resistance were more startled by negative pictures," says Willette, adding, "By extension, they may be more reactive to negative things in life."
"It is one piece of evidence to suggest that these metabolic problems are related to issues with how we perceive and deal with things that stress all of us out," he points out.
A vicious cycle
Also, the results of EEG tests performed on participants when their brains were at rest — that is, not engaged in any specific tasks — indicated that those with type 2 diabetes or prediabetes presented more activity in the right half of their brains.
This is interesting because an overactive right hemisphere has been
Wolf notes that the results suggest an explanation as to why people who have chronic metabolic diseases tend to find it so difficult to pursue a more healthful lifestyle to support them in their journey toward improved well-being.
If a person is consistently focused on negative thoughts, she says, they may find it hard to find the motivation to work toward a positive health outcome.
Moreover, the scientists found that participants with prediabetes and type 2 diabetes had low cortisol levels, which they read as a possible sign of chronic stress.
A telephone test of cognitive performance also established that these people had some cognitive deficits, such as poorer arithmetic ability.
The scientists argue that gaining a better understanding of how insulin resistance can contribute to an altered perception of stress factors could help specialists to counteract the effects of negative moods and thinking on patients aiming to overcome obesity and diabetes.
"For people with blood sugar problems, being more stressed and reactive can cause blood sugar to spike," says Wolf, noting that this sets up a vicious cycle.
"If people with prediabetes and diabetes are trying to reverse or treat the disease, stressful events may hinder their goals. Frequent negative reactions to stressful events can lead to a lower quality of life and create a vicious cycle that makes it difficult to be healthy."