A whole-body room calorimeter (also known as a metabolic chamber or respiration chamber) is an airtight room in which patients or trial participants reside for a set period of time, ranging normally from 24 hours to several days. Whole-body room calorimetry allows us to monitor subjects for such extended periods of time while in a free moving environment that permits differentiation of different components of energy expenditure such as sleeping, resting, physical activity as well as assessing the thermic effect of food.

The whole-body room calorimeter is continuously ventilated with “fresh air” and the expired gases by the study participants are mixed and extracted. Both inspired and expired gases are sampled to simultaneously determine oxygen consumption and carbon dioxide production. Over the time spent in the chamber, highly accurate analysis of the contribution of body fat, carbohydrate and protein to energy expenditure is therefore possible.

The system allows for a broad range of temperature settings which can be manipulated to examine the effect of different ambient temperature and humidity conditions on energy metabolism. However, in most settings temperature and relative humidity are kept relatively constant during a measurement period.

The layout is based on the Metabolic Research Unit Maastricht (MRUM), which is the result of 35 years of world-leading metabolic research. Key features include:

• fully equipped study room for multiple-day stay;
• extensive physiological and environmental data acquisition system delivering traceable raw data and calculated parameters;
• advanced environment control system (temperature, humidity, altitude);
• sampling interfaces (e.g. blood, urine, faeces, nutrition etc.);
• safety and communication features;
• industrial-grade components and installation;
• a modular system with extensions for environmental control (e.g. hypoxia, lighting), different room configurations, or additional physiological measurements (e.g. physical activity, ECG, heart rate, respiration rate, body temperature, skin temperature, blood pressure, blood glucose).

Obesity and type 2 diabetes

Obesity and type 2 diabetes are two metabolic risk factors and can lead to cardiovascular disease, the leading non-communicable disease in terms of premature deaths. Moreover, obesity and insulin resistance in women of reproductive age, in particular, not only increases the women’s own risk for future cardiometabolic disease, but also predisposes her offspring for adverse health outcomes. Lifestyle changes, including increased physical activity and a healthy diet are recommended as key preventive approaches of obesity and type 2 diabetes but many individuals fail to adhere to these preventive guidelines. New approaches are needed to capture the dynamics of acute and chronic interventions, which are important for changes to life-style or habitual behaviour.

Sleep and circadian rhythm

Research on the relationship between metabolic function and circadian biology is increasing dramatically, with the effects of our modern-day “round-the-clock” lifestyle linked to a rise in a number of metabolic conditions, including poor sleep patterns. In order to investigate fluctuations in daily circadian rhythms in response to various interventions (i.e., exercise, meal patterns, disruptions to sleep), whole-body room calorimeters provide the “gold standard” for investigating such phenomenon, due to the control of dark-light cycles and other environmental cues.

Exercise physiology and sports science

Physical activity, exercise training and the related metabolic and physiological benefits are of interest to sports scientists. Whole-body room calorimeters can be used to study both elite athletes’ and untrained individuals responses to exercise and dietary interventions.