Timed exercise, cold rooms and nutritionist-prepared meals are all part of a typical night in a Pennington Biomedical Research Center metabolic chamber.
Scientists in the 50 laboratories and 19 core research facilities at Pennington study chronic diseases through lab research and clinical studies. Among several subjects, researchers at the Center have made significant research discoveries regarding human nutrition and diabetes.
Pennington was a key contributor to the National Institute of Health-funded DASH diet studies. The U.S. News and World Report selected the DASH diet as the No. 1 diet program in the U.S. for three years.
A metabolic chamber, or whole-room calorimeter, assesses energy expenditure in a study participant over time. The participant’s metabolism of is measured while at rest, during physical activity, after eating and during sleep.
“We use it for studies as far as before and after medicines, before and after weight loss, before and after food, exercise,” said Crystal Traylor, a nurse practitioner at Pennington. “This has pretty much been the gold standard for determining energy expenditure for many years.”
Studies in the metabolic chamber can be done over 12 to 24 hours. Some studies require multiple visits to the chamber.
The chambers are small, enclosed rooms, designed like a hotel room for comfort. In each room, there is a bed, desk, television, phone, exercise bike, toilet, sink, small refrigerator and a metal “pass-through” box.
Pennington is building two new metabolic chambers: One will be similar to the other two at the facility. The other is a smaller chamber used for tests to determine “active” and “resting” metabolic rates in a shorter period of time.
“There’s a little bit better equipment, much more sensitive, but also much more time-consuming and not nearly as ‘push the buttons’ as the other ones,” Traylor said. “This smaller chamber that we have, nobody else has this entire setup like we have, in the world.”
The content of oxygen flowing into the chamber is controlled. As the participant inhales the oxygen and exhales, the carbon dioxide created by the body is collected through holes in the ceiling to be analyzed. Throughout the study, participants are required to provide urine samples, which are kept in a jug in the refrigerator.
The volume of carbon dioxide created by the body and the nitrogen content of the urine are analyzed and used to determine the energy expenditure of the participant. Results can take several weeks to analyze.
Before a study participant can enter the metabolic chamber, precise body weight and temperature measurements have to be taken to predict that person’s energy expenditure. Once the room’s heavy door is closed, it cannot be reopened until the study is finished.
In a 12-hour study, a participant will spend the first hour at rest on the bed but not asleep. This allows data for a resting metabolic rate to be captured.
The participant then peddles on the stationary bike for 30 minutes as moderate exercise. During this time, the data should reflect a rise in metabolic rate as the participant exercises.
After the “spontaneous physical activity,” the patient may sit at the desk on the provided laptop or lie on the bed and watch the television. An hour after the exercise portion, dinner is served.
The food for study participants at Pennington is prepared in the metabolic kitchen. In the kitchen, the dietitians make meals to meet the nutritional requirements of each study protocol. The kitchen is essential to producing valid scientific results in nutritional studies.
“Normally we want you to be eating the amount of food that we want you to be eating,” Traylor said. “We want you to be burning that same amount of calories so when you come out of the chamber it’s at zero, balanced. If we give you too much food or too little food, that may put your body into the unbalanced energy expenditure, and that can affect the results.”
Because the room must remain closed, the nurses pass water and food to the study participant in the chamber through the “pass-through” box in the wall. The nurse places a cup of water or a tray in one side of the box and closes it. When the box is closed, the participant unlocks and opens it on their side to remove the contents.
The participant must eat all of the food on the plate within 30 minutes, then send the tray back through the “pass-through” box. Data collected in the hours after the meal provides information on how the participant’s body reacts to calorie intake.
The participant in the metabolic chamber must go to bed and wake up at a certain time. The sleeping metabolic rate is determined over the course of the night.
According to Jennifer Rood, associate executive director for cores and resources at Pennington, the analysis of the data collected in the study will tell the researchers what the participant’s energy expenditure was, in kilocalories, during their stay. The study participants are given the analyzed data and a graph of their energy expenditure over the course of the study.
The research center uses the chambers for a study titled STARCH, which studies the effects of a slowly digesting starch in blueberry yogurt on the digestive system, metabolism and body fat of people with pre-diabetes.
Rood said the research done in the metabolic chamber is important for everyone.
“A healthier Louisiana starts with each of us,” Rood said. “The phenomenon of the ‘freshman 15’ is one that everyone has heard of. Better understanding our metabolism and how we can prevent this sort of weight gain can be an important tool in a college student’s tool box for their health.”

Gallery • 1 Photos

Sam Karlin

The Pennington Biomedical Research Center has four metabolic chambers to test for energy expenditure.