Metabolic Carts vs Metabolic Chambers

Breath-by-breath Indirect Calorimeter


When it comes to measuring metabolism, the majority of the medical world adopted an approach called breath-by-breath measurement. It is  probably the most common method to assess energy expenditure nowadays. Instrument like metabolic cart or potable calorimeter are in this category. They require the air going in and out of a subject being confined and analyzed.

So at each breath, the instrument can analyze the oxygen and carbon dioxide exchange, and produce the energy expenditure number. Thus most of these instruments look a bit claustrophobic, and are not suitable for studies to monitor energy expenditure for a prolonged time or more intricate metabolic studies, such as studies that involve:

  • Longer duration
    • Food-induced thermogenesis happens gradually 4 hours after diet
    • Sleeping
  • Environmental control
    • Cold-induced thermogenesis
    • Oxygen level control when studying hypoxia
    • Humidity control for exercise
  • More delicate activities
    • Eating
    • Instrument playing
    • Exercise requires freedom from wires (e.g. jumping rope, weight lifting)
  • Stress effect
    • Claustrophobic instrument could act as a confounding factor when studying the effect of stress on metabolism


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