“Room calorimeters do more than just measure energy expenditure”
–said Dr John Hattersley, Senior Research Fellow at the Human Metabolic Research Unit in the University of Warwick, UK.
During an informative sharing session at the Faculty of Health, Medicine and Life Sciences in Maastricht University two weeks ago, Dr Hattersley highlighted that whole-body room calorimeters measures energy expenditure, but is much more than just that. With over 20 years of research engineering experience and experience working with the Maastricht whole-body room calorimeters for a very diverse research group at the Metabolic Research Unit, he enthusiastically presented numerous important and unique research possibilities of studying human body responses in a natural, unrestrained setting with the whole-body room calorimeters.
The whole-body room calorimeter functions as a highly controlled environment for test subjects, with the ability to control temperature, humidity, light, sleep rhythm and many other factors. More importantly, data obtained from these whole-body room calorimeters can provide invaluable information which allows us to understand how the body uses metabolic substrates such as fats or carbohydrates in a range of environmental contexts.
The applications are extensive and include those shown in Tables 1 to 5.
Table 1: Base variables that can be investigated in combination with room calorimeters
| Base variables
Measurements provided directly via the equipment |
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| Name | Description | Equipment |
| Diurnal CO2 production | 1 Minute, 5 minute and 30 minute duration of human respiration volume of carbon dioxide produced. | Whole-body room calorimeters |
| Diurnal O2 Consumption | 1 Minute, 5 minute and 30 minute duration of human respiration volume of oxygen consumption. | Whole-body room calorimeters |
| Room Activity Levels | 1 Minute, 5 minute and 30 minute duration of room activity. | Whole-body room calorimeters |
| Body segment Activity Levels | Trial axial acceremeters attached to relevant body segment (e.g. sacrum, upper thigh, etc); resolution 25 or 100Hz | Accelerometers e.g. MOX activity monitors |
| Body temperature | Core temperature can be measured aurally, rectally or via skin- mounted sensors. | Various temperature sensors/ thermometers |
| All of the above can be applied in Normoxic or Hypoxic conditions, either using a metabolic cart or in the whole-body calorimeters. | ||
Table 2: Basic derived variables that can be analysed with room calorimeters and studies involving collection of human samples
| Basic Derived Variables
The following variables require intermediate analysis by the customer and are dependent upon the protocol used. Analysis required is simple statistical technique or linear equations. |
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| Name | Description | Equipment |
| Energy Expenditure | The energy expended by the subject on 1 min, 5 min and 30 min resolution. | Whole-body room calorimeters or Omnical |
| RER (or RQ) | The respiratory exchange ratio, often referred to as the respiratory quotient, defined as carbon dioxide consumed divided by oxygen consumption by the subject on 1 min, 5 min and 30 min resolution. | Whole-body room calorimeters or Omnical |
| Substrate Oxidation | Carbohydrate/ lipid/ protein oxidised during the experiment on 1 min, 5 min and 30 min resolution. | Whole-body room calorimeters or Omnical |
| Blood | Blood samples can be drawn periodically during an experiment allowing access to blood borne markers and analytes (e.g. insulin, glucose, FFA, etc); requires additional biochemistry. | Others |
| Sweat | Sweat samples may be taken directly from the skin or from AC unit sampling (e.g. sodium, nitrogen, etc); requires additional biochemical analysis equipment. | Others |
| Saliva | Saliva samples can be taken periodically from the subject using various methods (e.g. cortisol and testosterone); requires additional biochemical analysis equipment. | Others |
| Urine | Urine is collected to estimate protein oxidation it can also be used to determine other metabolic functions (e.g. glucose, ketone bodies, etc); requires additional analysis equipment. | Others |
| Each of the above variables can be measured over the physiological states defined in table 3, depending on the experimental protocol defined. These are only examples of what can be achieved. | ||
Table 3: Psychological responses that can be investigated in combination with room calorimeters
| Psychological Response | |
| Name | Description |
| Sleepiness/Alertness | Questionnaires to determine can be used frequently to assess participants’ sleepiness/tiredness (e.g. Epworth Scale, Standford Sleepiness Scale). |
| Satiety/Hunger | Visual Analogue Scores (VAS) are routinely used in studies to determine satiety and hunger. |
| Acute Mountain Sickness | AMS scores have been used to ensure safety during hypoxic studies. |
| Cognitive Profiling | Various computer based cognitive function tests can be employed during a study to investigate mental capabilities. |
Table 4: Complex derived variables that can be investigated in combination with room calorimeters
| Complex Derived variables
The following variables require intermediate analysis by the customer and are dependent upon the protocol used. Analysis required is simple statistical technique or linear equations. |
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| Name | Description | Equipment |
| Cost of physical activity | The metabolic cost of physical activity, at room level, assuming a linear relationship between activity and energy expenditure. | Whole-body room calorimeters |
| Diet Induced Thermogenesis (Total) | The metabolic cost of food digestion, total over the experiment. | Whole-body room calorimeters |
| Diet Induced Thermogenesis (per meal) | The metabolic cost of food digestion, for any meal consumed during the observation period. | Whole-body room calorimeters or Omnical |
| BMR | Basal metabolic rate, energy expenditure required at a cellular level, not constant over the observation period. | Whole-body room calorimeters |
| Dietary Intake (total) | The energy intake in the form of food during the experiment. | User defined |
| Dietary Intake (per meal) | The energy intake in any meal consumed during the observation period. | User defined |
Table 5: Physiological sates that can be measured with room calorimeters
| Physiological States | ||
| Name | Description | Equipment |
| SMR(1) | Sleeping metabolic rate as defined by the minimum 3 hr average. | Whole-body room calorimeters |
| SMR(2) | Sleeping metabolic rate as defined by the minimal physical activity. | Whole-body room calorimeters |
| SMR(3) | Sleeping metabolic rate as defined by the minimal residual method. | Whole-body room calorimeters |
| OMR | Overnight metabolic rate as defined as the average between 12:00 and 06:00. | Whole-body room calorimeters |
| RMR | Resting metabolic rate measured at rest, supine, fasted, emotional and thermally neutral. | Whole-body room calorimeters or Omnical |
| Fasted/Pre-prandial | Metabolic rate in the pre-prandial state, e.g. 12 hours fasted. | Whole-body room calorimeters or Omnical |
| Post-prandial | Dynamic metabolic response to food consumption. | Whole-body room calorimeters or Omnical |
| Thermic response | The energy requirements imposed to maintain thermal regulation under varying external temperatures. | Whole-body room calorimeters |
| Exercise | Energy expended during varying intensities and modalities of physical exercise. | Whole-body room calorimeters or Omnical |
| VO2 Max | Maximal aerobic capacity of the subject during exercise. | Whole-body room calorimeters or Omnical |
| HIIT | Metabolic output during High Intensity Interval Training sessions (e.g. Tabata Protocol). | Whole-body room calorimeters or Omnical |
| Through the use of addition methods (e.g. questionnaires, testing software) it is possible to gather information related to participants psychological response. These are only examples of possible variables. | ||
Maastricht Instruments whole-body room calorimeter is the most versatile system on the market that can be used for multiple applications. Along with ever-evolving research, the facilities in the rooms can be easily modified by changing settings or adding accessories. The analysis system, combined with the state of the art climate control enables users to perform a broad range of studies such as those shown in Tables 1 to 5: metabolism in relation to temperature, lifestyle, exercise, light etc. Blood can be collected through the air lock in the door, the freezing toilet collect all human waste for further analysis, the hands free intercom system allows easy communications with the subject (even while drawing blood), light conditions can be changed by adding additional color lights etc.
Other than whole-body room calorimetry systems, Maastricht Instruments offers other indirect calorimetry solutions such as the Omnical, a highly reliable, portable system that allows researchers to easily conduct various metabolic research studies (Tables 2 to 5).
Contact us to find out more about indirect calorimetry and our instruments.