Neural Mechanisms for Appetitive Responses to High Reward Foods

Completed

Brief Summary: This study is aimed at understanding neuroendocrine responses to different types of sugars and how this influences feeding behavior among lean, overweight, and obese individuals.

Detailed Description: The investigators have previously combined functional magnetic resonance imaging (fMRI) with hormonal and behavioral assessments to better understand the impacts of glucose and fructose on appetite and its central regulation in humans and have made important observations in lean individuals linking fructose consumption to overeating and obesity. The investigators now propose to expand this work by examining the impacts of glucose and fructose ingested together (sucrose), as occurs in real life, and by examining effects of a common non-nutritive sweetener, sucralose, on brain and appetitive response. The investigators propose a random-order crossover design to determine the effects of caloric and non-nutritive sweeteners among lean, overweight, and obese participants. The investigators will measure circulating levels of hormones involved in satiety signaling, quantify food intake, and measure brain activity using blood-oxygen level dependent and arterial spin labeling methods and functional connectivity analyses.

Recruitment & Eligibility

Inclusion Criteria

Age 18-35 years, right-handed, weight change <2% for at least 3 months prior to participation, no history of diabetes or other significant medical problems, fasting glucose <126 mg/dl.
Lean group: BMI of 19-24.9 kg/m2
Obese Group: BMI 30-40 kg/m2
Overweight Group: BMI of 25-29.9 kg/m2

Exclusion Criteria

Neurological, psychiatric or addiction disorder, fasting glucose ≥126 mg/dl, use of prescription medication (with the exception of contraceptives), tobacco use, contraindications to MRI scanning (detailed in Protection of Human Subjects), fructose intolerance, history of eating disorder, actively trying to lose weight.

Primary Outcome Measures

Name	Time	Method
Cerebral Blood Flow Response	Sessions 1, 2, 3, 4	Arterial spin labeling with be used to determine brain areas with relative increases or decreases in CBF after ingestion of sucrose, glucose, or sucralose.
Changes of Blood oxygen level-dependent (BOLD) signal responses to food vs non-food cues after ingestion of different types of sugar. BOLD signal responses to food cues will be compared at the level of whole brain and within a priori regions of interest.	Sessions 1, 2, 3, 4	These will be compared between ingestion of drinks and at level of whole brain and in regions of interest
Systemic Metabolite and Hormone Responses	Sessions 1, 2, 3, 4	The effects of sugar ingestion on changes in systemic metabolite (glucose) and hormone (insulin, GLP-1, leptin, ghrelin, peptide YY) levels will be assessed.

Secondary Outcome Measures

Name	Time	Method
Appetite Ratings	Sessions 1, 2, 3, 4	Ratings of hunger and desire for food in response to food vs non-food cues will be analyzed using a repeated-measures ANOVA with condition (glucose, sucrose, sucralose) and stimulus (food vs non-food) as within-subject factors.
Ad Libitum Food Intake	Sessions 1, 2, 3, 4	Total calories consumed and percent calories from sugar, fat and protein will be compared between conditions.
Functional Connectivity between regions involved in regulation of food intake	Sessions 1, 2, 3, 4	Investigators will perform a physiological-psychological-interaction (PPI) analysis using the nucleus accumbens as the seed to explore brain regions showing increased functional connectivity to the seed during the food-cue task.

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