Sugar on the Brain
High blood sugar levels are associated with low self-control.
Posted November 20, 2015
Picture this scenario: You’re healthy, but you’ve packed on some extra pounds over the years. Lately, your blood sugar levels have started creeping up a bit, too. They’re not in the diabetic range yet, and you want to keep things that way, so you vow to make better choices about diet and exercise. Yet somehow it seems harder than ever to walk past a box of doughnuts without grabbing one.
Sound frustratingly familiar? Yeah, it does to me, too. So my interest was piqued by a new study in Health Psychology, which looked at blood sugar levels and self-control in healthy individuals. The study showed that even slightly elevated blood sugar levels were associated with lower scores on a test of inhibitory control — the ability to hold back the first, impulsive reaction to a stimulus and respond in a more considered fashion.
In short, it’s not all in your imagination. When your blood sugar is already a little higher than normal, it's actually harder to resist reaching for a sweet treat.
A Test of Self-Control
The new study included 70 healthy, young adults, half of whom were obese. Their blood sugar was measured with a fasting blood glucose test. On this test, a blood sugar level of less than 100 mg/dl is considered normal. A slightly elevated blood sugar level of 100-125 mg/dl is considered prediabetic, and a high blood sugar level of 126 mg/dl or higher is indicative of diabetes. All the study participants fell below the diabetes cutoff point.
Inhibitory control was assessed using the go/no-go task. In this test, participants were presented with a series of X’s and O’s on a computer screen. They were asked to respond when they saw an X (which happened most of the time), and they were asked to withhold their response when they saw an O. Inaccuracy on this task indicates low inhibitory control.
“We learned that young adults who had prediabetic blood sugar levels combined with obesity — but who were otherwise very healthy — made the most errors on the go/no-go task,” says Misty Hawkins, Ph.D., lead author of the study and an assistant professor of psychology at Oklahoma State University. “These findings suggest that their inhibitory control was poorer than their peers who did not have elevated blood sugars.”
The Eat/No-Eat Task
In everyday life, low inhibitory control may affect how people respond — or don’t respond — when presented with food stimuli. “This study is small and cross-sectional, so we shouldn’t over-interpret the findings,” Dr. Hawkins cautions. “However, these findings could have important implications if we’re able to replicate them in a larger sample over time.” Specifically, the results suggest that people trying to make healthy eating choices may struggle more with self-control when their blood sugar is in the slightly elevated range, compared to lower blood sugar.
What happens when your brain habitually says “go” rather than “no go” around the cookie jar? You tend to gain weight. Obesity increases your risk of developing even higher blood sugar levels, which may eventually cross the threshold to type 2 diabetes.
Over time, type 2 diabetes that is not controlled with lifestyle changes and medication may affect cognition in more profound, lasting ways. “Many previous studies suggest that persons with type 2 diabetes have a faster rate of cognitive decline and a higher risk of developing dementia compared to the general population,” Dr. Hawkins says. Although researchers are still sorting out the connection between uncontrolled type 2 diabetes and impaired cognition, chronically high blood sugar and insulin resistance are possible contributing factors.
Can’t Can Resist”
Clearly, the earlier you interrupt this downward spiral, the better. Just recognizing the challenge may make you more cognizant of your actions. Beyond that, taking steps to keep your blood sugar at a healthier level may improve your self-control.
According to the National Institute of Diabetes and Digestive and Kidney Diseases, it’s often possible to reverse prediabetes or to prevent or delay type 2 diabetes by:
- Losing weight, if you’re overweight
- Increasing daily physical activity
- Decreasing calories and saturated fat
Dr. Hawkins says, “What our findings suggest to me is that interventions to help regulate blood sugar may also help promote healthier eating. People’s brains will be better able to resist unhealthy foods when their blood sugar levels are better regulated.”
Linda Wasmer Andrews specializes in writing about the intersection of health and psychology. Follow her on Facebook and Twitter. Read more from her blog:
Born to Be Junk Food Junkies
Cranberries Are a Smart Choice for Your Brain
How to Teach Yourself to Actually Like Vegetables