Human Energy Expenditure Sub-Core
(PI: Kuan Zhang, Ph.D.)
Definition of the core
The Energy Expenditure (EE) Laboratory has been in operation since 1996. It is an enormous asset to investigators for this facility as the techniques for assessment of energy expenditure and physical activity are technically challenging to establish and expensive to operate. It would be highly impractical, for example, for a single investigator to build and operate a human respiratory chamber for his/her exclusive use. In addition to maintaining the facility and providing testing services, the EE Core will provide consultative advice to investigators on tests that can be done and how to interpret the results. In addition, the EE Core will be a training opportunity for students, post-doctoral fellows, and both junior and senior investigators.
Objective of the core
The objective of the Energy Expenditure SubCore Laboratory is to make available to NYORC investigators a variety of techniques that are of interest in the study of obesity, eating disorders, and related problems. These services are best provided in a Core Laboratory because they require special instrumentation and methodology which would be difficult or impractical to establish in the laboratories of the individual investigators who are Users of the NYORC.
In investigations of ingestive behavior, efficiency of energy use, hormonal action, dietary intervention, molecular genetics, or drug effects, it is essential to be able to assess energy expenditure. It is often helpful to also assess substrate utilization and free-living physical activity. It may be useful to correlate these patterns with other phenomena, subjective or objective, relevant to the hypotheses being tested.
In subjects who are losing or gaining fat on different regimens, it is important to have information about how energy expenditure, substrate utilization and physical activity change. A full understanding of energy balance is impossible without assessment of these parameters.
Specifically, the objectives of the Energy Expenditure Core are:
Organization, Administration, and Management of the core
Director: Kuan Zhang, Ph.D.
The Energy Expenditure SubCore is under the Directorship of Dr. Kuan Zhang. Dr. Zhang administers and supervises three components of Core activities: human energy expenditure, physical activity measurements and the animal body composition and chemical analysis laboratory. He has been a contributor to the field of energy metabolism since 1996. He was one of key persons in building the whole-room calorimeter at St. Luke's-Roosevelt Hospital Center and first person who intensively conducted clinical testing, calibration and validation of a state of art device: Intelligent Device for Energy Expenditure and Activity (IDEEA). Dr. Zhang oversees all activities within the Core components he directs.
Overview of techniques and Services Offered
The EE SubCore component has three main areas of activity: 1) resting metabolic rate/substrate evaluation; 2) 24-hour energy expenditure/substrate oxidation and energy and nutrient balance assessment; and 3) free living assessment of physical activity and energy expenditure. The Core Laboratory provides the following services to cooperating investigators (Users), namely, measurement of:
| Table II-14 Test | Method | Ref |
|---|---|---|
| 24-hour energy expenditure/substrate oxidation, and energy and nutrient balance assessment. | VO2, VCO2, RQ, and energy expenditure in various resting, sleeping and exercise states and in response to a meal or exercise. | Ferrannini, 1988; Ravussin et al, 1986; Livsey e al, 1988; Brower et al, 1987 |
| Mechanical Work | Force Platform in metabolic chamber | Zhang, KMay, 2002 |
| Resting metabolic rate/substrate evaluation. | VO2, VCO2, RQ, and energy expenditure in the resting state. | Ferrannini, 1988; Ravussin et al, 1986; Livsey e al, 1988; Brower et al, 1987 |
| Urinary N and diet analysis (fat, N and energy) | See Chemical Analysis Laboratory in Animal Body Composition, Section. | |
| Free-living spontaneous physical activity and energy expenditure. | IDEEA (MiniSun, Inc., Fresno, CA) | Zhang et al. 2003; 2004 |
Core Management
i. Quality Control
There are numerous individual tests offered by the Core's laboratories. Quality control procedures are carried out for each test. Table II-15 shows the broad procedures presented below (abbreviations defined at bottom of table).
| Core | Table II-15 TEST | Quality Control Procedure(s) |
|---|---|---|
| EE | RMR & 24 hour energy expenditure | Calibration using standard gases; gasometer calibration of pneumotachometer; alcohol burning; inter-comparison between instruments |
| EE | Mechanical work | Calibration using weights on each square of a grid covering floor surface (Zhang, May 2002) |
| EE | Free-living PA and EE (IDEEA) | Validated against a series of timed standard activities (Zhang et al, 2003; 2004). |
Abbreviations: EE, Energy Expenditure; RMR, Resting Metabolic Rate; PA, Physical Activity; IDEEA: Intelligent Device for Energy Expenditure and Activity.
ii. Procedures
The procedures outlined above have been set up in the Core Laboratory and validated by established techniques. The Core Laboratory ensures excellent quality control for the procedures as well as the benefits of interaction between the cooperating investigators and the staff of the Core. It will be of distinct benefit to have the methods of the EE Core available through the NYORC.
iii. Prioritization of investigator use
Any investigator who wishes to have samples analyzed must submit a User's Request to the Laboratory Director. This request requires the investigator to identify the project, the type of funding and peer review of the project, the IRB approval, the number of samples to be analyzed, and the time constraints. Priority is given to young investigators. Investigators with P/F funded awards get first consideration. Other Users are selected based on scientific merit of the proposal and its relevance to obesity and eating disorders. There is a provision for establishing priority if the Core is overstressed. This is done by the Internal Advisory Committee in consultation with the Core Director. If there are disagreements between Users and the Executive Committee, the External Advisory Committee can be a final arbiter. Due to the limited budget available from the ORC for this Core, a charge-back system will be used, with little or no cost to young investigators with P&F grants.
Adapting to new technology
Advances in this Core component are proceeding rapidly in response to the increasing demand for high-accuracy, 24-hour studies. The respiratory chamber indirect calorimeter was previously re-designed and validated by Dr. Boozer working with Dr. Ming Sun, our biomedical engineering consultant, and Kuan Zhang, then a Columbia Engineering doctoral student. The original 3-room chamber design was reconstructed to form two separate live-in chambers. One chamber, with a force-transducer platform floor, is now used for 24-hour studies. The second chamber is used for RMR assessment and for short-term tests of EE during physical activity (stepping, cycling, running on treadmill, etc.). These indirect calorimetry facilities were used recently by Drs. Boozer and Zhang to validate a novel device for assessment of physical activity and energy expenditure in free-living individuals. The device, IDEEA (Intelligent Device for Energy Expenditure and Acitivty, MiniSun, Inc, Fresno, CA) was developed by our Consultant, Dr. Ming Sun. With the addition of this device, the Core is now able to assess EE and physical activity under many conditions from resting to free-living. These techniques are of value to many investigators at the NYORC and elsewhere, who are interested in the effects of diet, genetics, and physical activity on energy regulatory systems. The laboratory also serves as a teaching facility for a broad range of students and international visiting scientists.
The range of techniques available allow nutrient and energy balance studies in both normal and disease states such as thyroid abnormalities or wasting (eg Huntington's Disease, [Gaba, 2005]). They also make possible determination of factors contributing to obesity, study of the effects of normal life processes (e.g., aging and pregnancy, [Landsberger, 2005]) on energy balance and analysis of the effects of various treatments for obesity on substrate oxidation and EE.
In addition to quantifying energy expenditure, energy and substrate balance studies require analyses of food, urine, and other biological materials. These are carried out at the NYORC's Energy Balance Chemistry Laboratory, which is also under the direction of Dr. Boozer.
Facilities
All of the energy expenditure studies and chemical analyses are carried out at the New York Obesity Research Center's main location on the 9TH and 10th floors of the Babcock Building. These laboratories are under the direction of Dr. Zhang and there are two separate units: 1) a human respiratory chamber indirect calorimeter laboratory and related metabolic carts; 2) IDEEA monitors; 3) 2) a chemistry laboratory for animal body composition and food/biological material analysis (see Animal Phenotyping Core for description of this Laboratory).
The human respiratory chamber is located on the 9th floor of the North Block of the Babcock Building in the General Clinical Research Center, one floor below the NYORC laboratories. The metabolic kitchen is located across the hall from the respiratory chamber. Metabolic carts are also available at the NYORC laboratories. The Energy Expenditure component of the Core is closely affiliated with the Hormone-Metabolite/Mass Spectroscopy Core. Doses of doubly labeled water for energy expenditure studies are prepared and samples are collected at the New York Obesity Research Center. The samples are then delivered to Dr. Ginsberg's laboratory at the Columbia University for analysis.
The chemical laboratory, also located on the 10th floor of the Babcock Building, performs animal body composition and energy content analyses. The laboratory provides direct chemical analysis of body composition of small animals and composition of food, diet, urine, and stool. This laboratory also provides measurement of the energy value of specimens by direct (bomb) calorimetry.
Energy-nitrogen balance studies are carried out both in humans and in small animals. This method, considered the most sensitive and accurate procedure for estimating the composition of small body weight changes, has been used at the NYORC for more than 25 years and has advanced with new and updated calorimetry equipment.
The core lab have equipped with 26 IDEEA (Intelligent Device for Energy Expenditure and Activity) devices, the most comprehensive system for measuring physical activity under free-living conditions.
Equipment in the Energy Expenditure Laboratory includes: 24-h Chamber with force platform, Hood room, Instrument Room and Metabolic Carts.
Chamber: The respiratory chamber is an air-tight room (22,000 liter volume) equipped with a bed, chair, desk, television, VCR, radio, telephone, bicycle, sink, and toilet. The temperature of the room is maintained at 23°C ± 0.2°C. A fan draws mixed-air (sample air) out of the chamber, while fresh air (reference air) is forced into the chamber by the resulting negative pressure. A flow meter measures the flow rate; aliquots of entering reference air as well as of exiting sample air are collected continuously. The air samples are dried and analyzed by differential oxygen (Magnos 4G) and carbon dioxide (Magnos 3G) analyzers (both Hartman-Braun, Frankfurt, Germany). Actual oxygen consumption and carbon dioxide production are calculated as the difference between the composition of the entering and exiting air. The results are corrected for barometric pressure, flow-rate and humidity. A stationary bicycle is also connected to a computer for the recording of exercise. Data are recorded every ten seconds and are averaged over two minute intervals. The over all accuracy of the system for both EE and RQ measurements was evaluated by 15 pure alcohol (99.5%.) tests. The average time per test was 1381±126 min (mean ± SD). The percentage of computed VO2 versus the VO2 required to oxidize the amount of alcohol burned was 98.48 ± 0.82% (mean ± SD), C.V. = 0.0083; the percentage of computed VCO2 recovered was 98.58 ± 0.84% (mean ± SD), C.V. = 0.0085. The measured RQ was 0.6675 ± 0.0029 (mean ± SD) versus 0.6666 calculated, C.V. = 0.0044. From the relatively small SD in computed VO2 and accurate average RQ, we conclude that the error for EE measurement was within 2.0%.
Force Platform: Mechanical work due to the physical activities of the subjects in the chamber is measured by a force platform (9´ x 6.5´) that rests on four force transducers that measure forces in the vertical direction. Except for time exercising on a stationary bicycle and using the toilet, the subject remains on the force platform the entire time while in the chamber. The four transducers measure the ground reaction forces generated by the subject for each movement. The position of subject and mechanical power spent for the movement is then calculated by using equation that have been previously described (Zhang, Appendix 3). The force platform not only detects displacements of the center of mass, but also calculates how much external mechanical work is done during the movement. As with the oxygen and the carbon dioxide data, floor data are collected continuously, analyzed every ten seconds and averaged over two-minute intervals.
Hood Respirometry Measurement Room: This separate room contains a bed, a treadmill, a stationary bicycle and a step platform. Separate hoods are used to collect expired air from subjects lying on the bed (for RMR determinations) or from exercise tests. The sampled air is then directed to a separate set of CO2 and O22 gas analyzers in the instrument room, where data is collected on a computer devoted to data collection from these tests.
Instrument Room: This room contains two sets of oxygen and carbon dioxide analyzers (Hartmann Braun, Frankfurt Germany) and all of the flow meters, filters and other devices involved with sampling, drying and measuring air for the 24-hour and hood indirect calorimetry tests. The Chamber and Hood measurement systems are independent and can be run simultaneously. Data is collected on two separate computers devoted to that purpose. One additional computer continuously monitors temperature control in the Chamber and a fourth computer collects data from the stationary bicycle in the Chamber.
Metabolic Carts: There are three metabolic carts located in the body composition laboratory: 1) DeltaTrac II Metabolic Monitor, Sensormedics Inc.; 2) MedGem®, Healthetech Inc.; 3) CPX Express, Medical Graphics Inc. Two more metabolic carts (DeltaTrac II Metabolic Monitor, Sensormedics Inc.) are located in the GCRC. All five of these are available to the EE SubCore for additional RMR determinations.
The facilities are all located near each other, in close proximity to Dr. Boozer's office, and are directly associated with the Hospital's metabolic unit. A metabolic kitchen for preparation and weighing of food and leftovers is located across the hall from the respiratory chamber. A nurse's station located nearby provides 24-hour support to subjects in the chamber.
IDEEA devices: A new microcomputer-based portable physical activity and energy expenditure measurement device. The current IDEEA system consists of one recorder (58 grams) and five small sensors (each 16 x 14 x 4 mm, about the size of a small postage stamp) that are placed on the chest, the frontal part of each thigh, and under each foot (Figure 1). The sensors are connected to the recorder by thin and flexible wires (1.8mm outer diameter). Before the test, sensors are applied to body locations by hypoallergenic tape, and the IDEEA recorder connected to a personal computer by a communication cable. A windows-based interface program controls the communication between IDEEA and a laptop or desktop computer. After entering the filename, weight, height, age, gender, an optional study ID and short memo from the keyboard of the PC, the cable can be detached and the IDEEA started to begin to collect data. At the end of data collection , IDEEA can be power off. Data will remain in IDEEA until loaded onto a computer.
These motion signals are first pre-processed by signal conditioners. The output electric signals representing motion and speed are then fed at high rate through a cable to the microcomputer data acquisition unit. The multi-channel raw data are temporarily stored in the random access memory (RAM). They are then further processed by the microprocessor and stored in flash memory together with specific events and the subject's characteristics (age, gender, body weight, height and estimated fitness level). These data are downloaded to a computer for analysis at the end of each test. IDEEA can operate for up to 7 days. The outputs of IDEEA provide the specific type (e.g., sitting, climbing stairs, jumping etc.), duration, and estimated intensity if applicable (such as the speed of walking and running) of daily activities on second-by-second basis (ranging from milliseconds to hours).
The ability of IDEEA to correctly identify type, onset, duration and intensity of activities allows the estimation of EE in free-living conditions. EE is estimated by 4 major categories of inputs: 1) RMR calculated according to demographic information; 2) The types of PA; 3) The intensity IDEEA of activity such as the speed of walking and running; and 4) The position, speed and acceleration of trunk and limbs. These variables are used as inputs to a model that is constructed using the System Identification and Artificial Neural Network methods. EE is calculated as the output of this model. The computed EE is then compared with the EE measured through indirect calorimetry techniques, and the parameters of the model are modified according to the directions of error gradients in a multi-dimensional error space. The best model with minimum errors, in a least-square sense, which is applied to the validation data sets, is selected as the final model.
The IDEEA has the following major functions:
The charge for using Human Energy Expenditure Core
| Funding resources |
| Hood calorimeter ($) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| NIH |
| 150 | ||||||||||||
| Non-NIH |
| 175 | ||||||||||||
| Other | Decided case by case, must be funding and publication oriented | |||||||||||||
* Technician is only available between 8:00 AM and 4:00 PM from Monday to Friday. The technician is not a research assistant and only responsible for the chamber operation and subjects feeding. Research protocol should be supervised by investigators or research assistants.
** Measurement during working hour (8:00 AM ~ 4:00) is considered as half day. Any measurement beyond that is considered as 24-hour measurement.
Teaching and Training
The Energy Expenditure Laboratory will have a strong training and teaching function. In the past five-year cycle, it has welcomed into its laboratories a number of investigators who wished to partake of the expertise of the staff in technical knowledge. We try to impart knowledge not only of the specific methodology required, but also of its theoretical framework. This is done through personal mentoring and discussion and also assigned reading. We also provide help in analysis and interpretation of results for those individuals who are new to specific testing.
The Core Laboratories serve as educational facilities for students at all levels of training. Many of the Center's research projects are focused on ethnicity, body composition, energy expenditure, and obesity and the students have a diversity of ethnic backgrounds. Many U.S. and foreign scientists come to the New York Obesity Research Center seeking training in the use of equipment and techniques.
Contact Information
Kuan Zhang, Ph.D.
Obesity Research Center: Babcock 1017
St. Luke's-Roosevelt Hospital Center
1111 Amsterdam Avenue
New York, NY 10025
Tel:(212) 523-4176 (office); -234994 (chamber)
Fax:(212) 523-4830
E-mail: kz6@columbia.edu