This study plans to learn more about how age and weight impact appetite and food intake. Specifically, this study is being done to see whether age and obesity impact appetite and the brain's response to food. In this study the investigators will be evaluating how participants brains respond to food images as well as your food-related behaviors and hormones. The investigators will be comparing older individuals aged 65 to 85 years who are normal weight compared to those who are obese. The Investigators will then compare older aged individuals to younger adults aged 21 to 45 years.

In a cross sectional design participants will be studied on one occasion after a 3-day diet run-in. On the study day they will present in the fasting state, have an intravenous catheter placed for blood draws and have baseline blood samples taken and appetite measures performed. Participants will then undergo functional magnetic resonance imaging (fMRI). This will be followed by a breakfast meal. Blood and appetite measures will be performed every half hour for 3 hours. Repeat fMRI will be performed 30 minutes after the meal. After three hours participants will be offered a buffet style lunch and then will be done with the study visit.

Inclusion Criteria:

• Older aged adults (O): 65-85
• Younger adults (Y): 21-45
• Obese (Ob): body mass index (BMI) 30-40
• Normal Weight (NW): BMI 18-25

Exclusion Criteria:

• Pregnancy;
• Advanced organ failure;
• Active cancer diagnosis;
• Uncontrolled hypertension or metabolic disorder;
• Cognitive impairment or psychiatric disease limiting ability to comply;
• Presently in an exercise or diet program;
• Recent weight loss of >5 lbs in past 6 mo.;
• Bariatric surgery;
• Use of any weight loss drugs;
• Use of any medication known to significantly affect appetite (anti-depressants are allowable);
• Present tobacco use;
• Use/abuse of substances of abuse including any marijuana use by history;
• Any contraindication to MRI;
• Claustrophobia;
• Body weight >300 lbs; and
• Inability to fit in MRI scanner.