The purpose of this study is to use magnetic resonance imaging (MRI) to evaluate the human hypothalamus for signs of inflammation in response to specific diets. This research may lead to a better understanding of how poor nutritional quality may lead to obesity through effects on regions of the brain known to regulate body weight.

Inclusion Criteria:

• Age 20-40 years
• Overweight: BMI 25-29.9 kg/m2
• Willing to undergo randomly assigned 14-day diet modification

Exclusion Criteria:

• History of bariatric surgery or active participation in weight-loss program
• Major medical or neurological disorder (e.g., diabetes, multiple sclerosis)
• Anemia or impaired kidney or liver function
• Known gallbladder disease or gallstones
• Hypertriglyceridemia (>350 mg/dl)
• Current use of orlistat or other weight-loss medications or other medications known to alter appetite (e.g., atypical anti-psychotics)
• More than moderate level of physical activity (>1000 met-min/wk)
• Pregnancy, menopause, or breastfeeding
• MRI contraindication (e.g., implanted metal, claustrophobia)
• Lifetime eating disorder
• Current smoking or heavy alcohol use (≥ 2 drinks per day for females and ≥ 3 drinks per day for males)
• Weight > 350 pounds (MRI limit)
• Dietary restrictions (e.g., vegan) incompatible with controlled diets