Scientists have studied how fasting and nutrients affect brain function in animals. The purpose of this study is to look at the effects of both fasting and food intake on brain function and memory in humans. To do this the investigators will use functional MRI to observe the brain and its function while fasting and after a meal. Understanding the action of these hormones in the brain may eventually lead to new ways to help people avoid obesity or lose weight.

Potential subjects will participate in a short phone screening interview and if eligible, will come to the University of Washington hospital 2 times. At the first health screening visit, we will go over the subjects' medical history, weight and height, and eating habits. This visit will take an hour or so and eligible subjects will then schedule the study visit. For the study visit, subjects will have to fast overnight from 9:30 pm the night before and arrive at the hospital at 8:00am. At 8:30 am, the subject will have a 30 minute MRI scan of the brain done in the University of Washington Radiology Department. During the MRI scan they will see pictures of common objects and foods and be asked to remember the photos they saw. At 9 am subjects will eat a standard breakfast, and they will not eat again until after the second MRI. The time of their second MRI will be randomly assigned to one of seven time points anywhere from 15 minutes to 5 hours after the breakfast. After the MRI, subjects will be allowed to eat freely from food we provide. Subjects will receive $10 for the health screening visit, and $50-85 depending on the length of the visit.

Inclusion Criteria:

1. Age 18-50

2. Body mass index (BMI) 18.5-24.9 kg/m2

   • Age and weight are restricted because of known changes in appetite and satiety with aging and changes in body weight.

Exclusion Criteria:

1. Current dieting for weight loss or restrained eating

2. History of eating disorders, prior obesity, or weight loss surgery

3. Chronic health conditions, including diabetes

4. Use of medications that alter appetite (e.g., atypical anti-psychotics)

5. Pregnancy or use of oral contraceptives of estrogen replacement

6. Participation in other studies that might affect appetite or body weight

7. Recreational drug use or alcohol use of >2 drinks per day

8. Food allergies to study foods or inability to taste

9. Current smoker

10. Any contraindications to MRI such as implanted metal of claustrophobia

    • Current dieting, restrained eating, eating disorders, prior weight loss surgery, diabetes, chronic disease (e.g., cardiovascular disease, cancer), and estrogen use are restricted or excluded due to documented influences on the hormones of interest. Smokers and regular alcohol users are excluded consistent with prior studies of appetite regulation.

We will enroll 21 healthy subjects. Participants will be recruited by flyers posted at the University and by newspaper advertisements.