by
Carol Ko, Staff Writer | June 13, 2013
Dr. Gene-Jack Wang,
lead author of the study.
Obese patients who have trouble controlling their diet might be comforted to know it may not all be in their heads.
A new study presented at the SNMMI 2013 Annual Meeting may show that patients with insulin resistance release lower-than-normal levels of dopamine when eating calories, leading patients to compensate by consuming extra food.
An estimated one-third of Americans are obese, and about 26 million Americans are living with diabetes, with another 79 million thought to be prediabetic.
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This chemical response may go some way toward explaining how food-reward signals contribute to obesity and help inform future interventions for patients at risk for becoming obese.
"A better understanding of the cerebral mechanisms underlying abnormal eating behaviors with insulin resistance would help in interventions to counteract overeating and obesity," said Dr. Gene-Jack Wang, lead author of the study and chair of the medical department at Brookhaven National Laboratory in New York.
Researchers had 11 healthy patients and eight insulin-resistant patients consume a glucose drink on one day and an artificially sweetened drink the next. Prior studies on animals showed that consuming calories releases dopamine in the brain, stimulating regions associated with reward and pleasure.
After each drink, the patients were scanned with PET machines and injected with an agent that helped visually trace dopamine. Researchers were then able to map dopamine levels in the brain.
Insulin-resistant patients with disorderly eating released significantly lower levels of dopamine in response to the drink with calories when compared to healthy patients.
These new findings may also lend credence to other studies that show artificial sweeteners are associated with weight gain. For example, researchers at Purdue University's Ingestive Behavior Research Center found that rats that ingested artificial sweeteners consumed more calories and put on more weight than rats that ingested table sugar.
If overeating is driven by a lack of dopamine during calorie ingestion, then no amount of artificial sweeteners would help compensate for that dopamine deficiency.
Though this study shows that insulin resistant patients have abnormal dopamine responses to calories, the primary cause behind insulin resistance and overeating is still unknown.
