Metabolic Clinical Research Unit Research Areas
Studies at the MCRU focus on factors that impact body weight regulation and metabolism and employ the following research studies:
Every person is composed of bone, muscle, organs, water, and fat. The study of body composition looks at an individual’s percentage of lean mass (bone, muscle, organs, and water) and fat. Some fat is necessary for overall health because it plays an important role in protecting internal organs, provides energy, and regulates the hormones that perform various functions in body regulation. Excess fat, however, has been linked to a number of health problems such as an increased risk of cancer, diabetes, and heart disease. Body composition tests help us develop personalized nutrition and exercise programs.
- DXA (dual-energy x-ray absorptiometry) Scan - This is a medical imaging scanner, similar to an x-ray, that uses very low dose x-rays to obtain detailed images of the bones, lean body mass, and body fat of participants. In this test, participants lay flat on a raised, padded bed while a scanning arm moves slowly over them.
- BodPod - This is used to provide a whole-body measurement of body volume. Together with weight, this is used to determine the overall lean and fat mass in a participant. In this test, participants sit inside a capsule, while computerized pressure sensors determine the amount of air displaced by their body.
- Bioelectrical Impedance - This test is based on the idea that lean tissue allows electrical current to pass through it more easily than fat tissue, because it has higher water content. To determine a participant’s body fat mass and total body water content, we place electrodes on the participant’s hand and foot and send a low dose electrical current through their body. This current is so small that most participants cannot feel anything.
The MCRU’s exercise testing lab is used to assess personal fitness levels.
- Exercise Testing Lab - We measure a participant’s oxygen consumption and heart rate during various intensities of physical activity on treadmills or stationary bicycles. The exercise testing lab is also used to monitor respiratory status and metabolic rate during studies involving longer exercise interventions.
Nutrition and Diet
An important part of understanding weight regulation is focused on studying how much and what people eat. Weight gain occurs when the amount of energy we take in from our food is greater than the energy our bodies use over time. The food and drink that we consume is converted by our bodies into energy that is needed for bodily processes or for physical activity. Food consumed that is not needed to meet energy needs is stored as fat. As we do things throughout the day, we use this energy. Some activities, like breathing and sleeping, use very little energy. Other activities, like walking or running, use more energy.
- The Metabolic Research Kitchen - In some of the research studies conducted in the Metabolic Clinical Research Unit, our metabolic research kitchen staff prepares controlled meals for study participants.
- Food Preference and Eating Behavior Studies - The MCRU uses a variety of methods to study what, when, and how much people choose to consume. We want to better understand what influences these decisions. Subjects may be asked to fill out various questionnaires about their eating habits or write down what they eat for several days. They also may participate in studies where they actually choose what, when, and how much they eat in a test situation.
- Food Arrays - Studies using food arrays allow researchers to investigate choices people make when presented with a wide range of foods. Subjects choose foods much like what they would from a buffet-style meal. The dietitians then analyze the subject’s choices to better understand eating behaviors. Current studies are looking at food choices in both children and adults.
- Computerized Vending Machines - The MCRU has three specialized vending machines. These machines can be stocked with a wide range of foods such as juices, milk, fruits, vegetables, sandwiches, potato chips, yogurt, various desserts, and other choices. These vending machines are useful to see when and what people choose to eat when they are participating in a study.
Metabolism is closely linked to body weight. For essential functions of our body such as maintaining temperature, breathing, and circulation, calories are taken from the foods we eat and energy we store fat. As we do activities throughout the day, such as walking, climbing stairs, household tasks or exercising, we use more energy. There are different ways to measure the energy we use.
- Whole-Room Respiratory Suites - This instrument is capable of determining energy expenditure during sleep, rest, meals, exercise, and other conditions. It continuously measures the oxygen you inhale and the carbon dioxide you exhale.
- Metabolic Carts - A metabolic cart is used to measure the oxygen you inhale and the carbon dioxide you exhale during rest, after meals, and during certain exercises. Metabolic carts can measure changes in oxygen and carbon dioxide on a breath by breath basis.
- Doubly-Labeled Water - Participants are given special water where some of the hydrogen and oxygen atoms are replaced with non-radioactive and non-toxic isotopes. The concentrations of the isotopes are measured over time by sampling saliva, urine, or blood. This determines a participant’s energy metabolism.
This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.