This study will describe the phenotype (physical and behavioral traits) of overweight and
obese people. It will characterize the hormones, metabolism, food preferences, fitness and
physical activity levels, sleep patterns and thought processes in people with and without
weight problems. Genetic material will be collected for studies of the internal codes that
influence body weight.
People over 18 years of age from all weight categories (lean, overweight, obese) who are
reasonably healthy may be eligible for this study. Participants undergo the following tests
- Physical exam, electrocardiogram, blood and urine tests, instructions for recording food
intake for 7 days
- Metabolic studies for menstruating women.
- Resting metabolic rate to study how many calories the body burns at rest.
- Mixed meal test to measure hormones such as insulin that regulate blood sugar.
- Glucose tolerance test to determine how sensitive the body is to insulin.
- 24-hour energy expenditure to measure the amount of oxygen breathed in and the amount of
carbon dioxide breathed out.
- Repeat 24-hour energy expenditure.
- Diurnal blood sampling and temperature assessment to study the body s internal clock.
- Air-displacement plethysmography (Bod Pod) to measure body composition.
- Dual energy x-ray absortiometry (DEXA) to measure body fat and bone density.
- Repeat Bod Pod and DEXA.
- Anthropometric measurements and bioelectrical impedance to measure height, weight, and
circumferences, skinfold thickness, fluid status and percentage body fat.
- Bromide dilution to measure the amount of water not in cells in the body.
- Doubly labeled water to measure the amount of calories burned in a 7-day period.
- 24-hour diet reports.
- Endothelial reactivity to measure how the blood vessels stretch or dilate for assessing
- Treadmill or bicycle exercise capacity test.
- Physical activity monitor.
- Unicorder to detect any breathing difficulties that may interfere with sleep.
- Fat and muscle biopsy to look for variations in gene expression in fat tissue and
- Neurocognitive testing to check memory, decision-making, hand-eye coordination, and
- Evaluation of mood problems and assess personality type.
- Evaluation to assess the quantity and quality of pain experienced.
- Taste testing to determine the response to bitter, salty, sweet and sour substances.
- Occupational therapy evaluation to explore the subject s adaptations, if any, for
performing personal, social or professional activities; the subject s views on his or
her weight, body size and shape, and strategies to control weight.
Hypoglycemia is the term used to refer to lower than normal levels of blood sugar. This study
will continue to research the causes of hypoglycemia.
Patients involved in the study will be admitted to the Clinical Center of the National
Institutes of Health and undergo tests for evaluating blood sugar. Patients will be required
to refrain from eating for a set period of time and will undergo blood tests for insulin
levels and several other specific diagnostic tests related to insulin secretion. The patients
will be under supervision and will be provided with appropriate medical and surgical
attention as needed.