Abstract
Emerging evidence from recent neuroimaging studies suggests that specific food-related behaviors contribute to the development of obesity. The aim of this review was to report the neural responses to visual food cues, as assessed by functional magnetic resonance imaging (fMRI), in humans of differing weight status. Published studies to 2014 were retrieved and included if they used visual food cues, studied humans >18 years old, reported weight status, and included fMRI outcomes. Sixty studies were identified that investigated the neural responses of healthy weight participants (n = 26), healthy weight compared to obese participants (n = 17), and weight-loss interventions (n = 12). High-calorie food images were used in the majority of studies (n = 36), however, image selection justification was only provided in 19 studies. Obese individuals had increased activation of reward-related brain areas including the insula and orbitofrontal cortex in response to visual food cues compared to healthy weight individuals, and this was particularly evident in response to energy dense cues. Additionally, obese individuals were more responsive to food images when satiated. Meta-analysis of changes in neural activation post-weight loss revealed small areas of convergence across studies in brain areas related to emotion, memory, and learning, including the cingulate gyrus, lentiform nucleus, and precuneus. Differential activation patterns to visual food cues were observed between obese, healthy weight, and weight-loss populations. Future studies require standardization of nutrition variables and fMRI outcomes to enable more direct comparisons between studies.
Highlights
The prevalence of obesity is increasing rapidly [1] with 33.6% of people in the United States classified as overweight and 34.9% classified as obese in 2011–2012 [2]
Emerging evidence from recent neuroimaging studies suggests that specific food-related behaviors contribute to the development of obesity.The aim of this review was to report the neural responses to visual food cues, as assessed by functional magnetic resonance imaging, in humans of differing weight status
OF THE Activation likelihood estimation (ALE) META-ANALYSIS As only one study reported increases in brain activation following weight loss, only studies reporting decreases in neural activation from pre- to post-weight loss were included in the meta-analysis
Summary
The prevalence of obesity is increasing rapidly [1] with 33.6% of people in the United States classified as overweight and 34.9% classified as obese in 2011–2012 [2]. Obesity increases the risk for a variety of lifestyle diseases including cardiovascular disease, hypertension, diabetes, and some cancers [3], as well as reduced quality of life [4]. To minimize the substantial economic and health burden of obesity, numerous approaches have been used to target overweight and obese individuals to facilitate weight loss, including lifestyle and surgical interventions [5]. There has been interest in the possible role that neural mechanisms play in the development and maintenance of obesity. Increasing attention has been given to investigating the impact these neural mechanisms may have on weight loss and maintenance
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