LOS ANGELES — Adults with a lower body fat percentage and lower 30-minute insulin levels performed better on a computerized gambling task after a meal than adults with higher body fat percentage or insulin levels, according to study findings presented at ObesityWeek 2015.
Douglas Chang, MD, PhD, of the National Institute of Diabetes and Digestive and Kidney Diseases in Phoenix, said short- and long-term changes in energy balance likely affected performance on the Iowa gambling task.
“Insulin and body fat, via leptin, acting both independently and together, may affect performance of a reward-related task in humans,” Chang said while presenting his findings.
Chang and colleagues analyzed data from 196 healthy adults with no active substance abuse and normal or impaired glucose regulation (mean age, 35 years; 128 men; 67 Native American; mean BMI, 32 kg/m2). During 5 days in a clinical research facility, participants underwent a DXA scan and completed the Iowa gambling task after breakfast or after lunch, and underwent an oral glucose tolerance test after at least 3 days of a weight-maintaining diet.
For the gambling task, participants chose one card at a time from four card decks (labeled A, B, C and D); the card selection results in the winning or loss of money. Decks A and B were considered “bad” decks, with an expected value of –$250; decks C and D were considered “good” decks, with an expected value of $250. The participants were instructed to win as much money as possible; the task ended after 100 cards were chosen.
The researchers found that age, sex, race, education, BMI and glucose were not associated with the participants’ scores on the gambling task, Chang said.
However, after multivariate analysis, both lower percent body fat (P = .008) and lower 30-minute insulin levels (P = .0007) were independently associated with a better score on the gambling task.
Data also pointed to an interaction between percent body fat and 30-minute insulin, Chang said. At high body fat, insulin had a lesser effect on the gambling score; at low percent body fat, 30-minute insulin had a greater effect on the score.
Researchers also measured peripheral leptin levels in 138 of the participants and found that lower leptin levels were associated with better gambling task scores.
“Since leptin and percent body fat are highly correlated ... we performed mediation analysis for percent body fat, leptin and [gambling task] score, and after accounting for leptin, association between body fat and [gambling task] score was almost completely suppressed,” Chang said. “Leptin, rather than body fat, independently determined [gambling task] performance.”
Additional multivariate analysis showed that lower leptin and insulin levels were independently associated with a better gambling task score, and there was an interaction between leptin and insulin, Chang said. The results persisted after adjustment for age, sex, race and education.
Insulin and leptin have been shown in previous studies to modulate the activity of dopaminergic neurons in the midbrain, and they have been shown to elevate reward thresholds and decrease food intake, Chang noted.
“So it is possible that insulin and leptin may modulate salience of the card decks, which serve as visual cues, and associations with money, which act as a reward, via these neural circuits.” – by Regina Schaffer
Chang D. Simple index of insulin secretion and body fat are associated with cognitive decision-making measured by the Iowa gambling task. Presented at: ObesityWeek; Nov. 2-6, 2015; Los Angeles.
Disclosure: Chang reports no relevant financial disclosures.