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.

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.

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.

Participants in the greater Los Angeles area will be recruited. Lean, overweight, and obese participants will be recruited.