Neural activation patterns in response to food-related cues

Limiting intake of high-fat and high-fat/high-sugar foods avoids the blunting of taste and reward responsivity to food, thus reducing risk for future weight gain.

Background: Weight loss strategies share a common core principle; that is to lose weight, calories must be reduced in one way or another. However, weight loss diets that solely emphasize energy restriction can be difficult to maintain and often fail to address eating behaviors that contribute to weight gain. 

There is considerable evidence that neural mechanisms play a role in governing eating behaviors such as overeating.  A better understanding of neurocircuitry has helped researchers recognize how regions of the brain respond differentially to various food-related cues. Neuroimaging techniques, such as functional Magnetic Resonance Imaging (fMRI), have helped identify neural activation patterns in response to food. 

Emerging data suggest that weight gain is associated with changes in neural response to palatable food tastes and palatable food cues, which subsequently may serve to maintain overeating. To test this hypothesis, researchers Sonja Yokum and Eric Stice (Oregon Research Institute) investigated whether weight gain is associated with neural changes in response to tastes of milkshakes varying in fat and sugar content and palatable food images.

Study results, published in the September 2019 issue of The American Journal of Clinical Nutrition, suggest that weight gain is associated with a decrease in responsivity of brain regions associated with taste and reward processing to palatable, high-fat- and high-fat/high-sugar foods.

Study Design:  Using fMRI, researchers compared changes in neural activity between initially healthy weight adolescents who gained weight and those showing weight stability. All participants completed the fMRI scan at baseline; 126 completed the second scan at 1-year follow-up, 119 participants completed the third scan at 2-year follow-up, and 119 completed the fourth scan at 3-year follow-up.

To determine whether sugar, fat, or the combination of both was more effective in recruiting reward neural circuitry, subjects received the tastes of the following milkshakes: a high-fat/high-sugar milkshake, a high-fat/low-sugar milkshake, a low-fat/high–sugar milkshake, and a low-fat/low-sugar milkshake.  To examine neural responses to imagined consumption of appetizing foods, unappetizing foods, and glasses of water, subjects were shown food pictures prior to the scan. During the scan, participants were exposed to pictures of food they previously rated as the most appetizing and as the least appetizing.

Results and Conclusions:  Adolescents who gained weight versus those who remained weight stable showed differing activation patterns in various regions of the brain in response to high-fat- and high-fat/high-sugar milkshakes versus low-fat/low-sugar milkshakes.  No group differences emerged in response to a low-fat/high-sugar versus low-fat/low sugar milkshake. Study results suggest that weight gain is associated with decreased responsivity of brain regions linked with taste and reward processing to palatable, high-fat- and high-fat/high-sugar food tastes.

Furthermore, elevated activation in taste processing regions of the brain to high-fat food tastes and elevated activation in a memory processing region to palatable food images were associated with future weight gain. The researchers speculate that an initial hyper-responsivity in taste processing regions to high-fat foods may increase risk for overeating a high-fat diet, which, in turn, may result in an attenuated sensitivity to dietary fat. In turn, a reduction in fat taste sensitivity may contribute to an impaired satiety response, resulting in excess high-calorie food consumption and unhealthy weight gain. These findings also suggest that avoiding weight gain by limiting intake of high-fat and high-fat/high-sugar foods avoids the blunting of taste and reward responsivity to food, thus reducing risk for future weight gain. 

Reference: Yokum S, Stice E. Weight gain is associated with changes in neural response to palatable food tastes varying in sugar and fat and palatable food images: A repeated- measures fMRI study. The American Journal of Clinical Nutrition https://doi.org/10.1093/ajcn/nqz204.

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