Indirect calorimetry

Your doctor may recommend performing an indirect calorimetry test to understand how much energy your body uses when resting. It’s also often used to measure carbon dioxide production, calculate oxygen use and provide a metabolic rate assessment.

Your Aurora specialist can use the results of an indirect calorimetry test to recommend changes to your diet to meet your energy needs and evaluate treatment for various heart and lung conditions.

What is an indirect calorimetry test?

Indirect calorimetry is often used by athletes to optimize nutrition and to determine calorie needs for both resting and during physical exercise. It has several clinical uses as well.

Doctors can get a detailed health assessment through calorimetry. It's considered the gold standard for:

• Determining how many calories your body uses
• Respiratory gas analysis
• Energy metabolism analysis.

Using an indirect calorimetry machine, your doctor can calculate the heat your body produces through carbon dioxide production or oxygen use.

Direct vs. indirect calorimetry

You may hear the term direct calorimetry used with indirect calorimetry. Both tests provide similar measurements, but direct calorimetry is more complex, lasts longer and usually costs more.

Direct calorimetry measures heat directly released from the body, usually within a calorimeter chamber instead of with a mask or mouthpiece.

The indirect calorimetry test process

An indirect calorimetry test is performed using a metabolic cart that includes a computer, blood pressure cuff and breathing mask. The setup of the test depends on the purpose of having the test done.

If your doctor is checking for resting energy expenditure, the test typically last 10 minutes and would require no physical activity. Your Aurora doctor may also tell you to not consume caffeine or other stimulants on the day of testing.

You'll be lying down or seated. A mask or mouthpiece that connects to the indirect calorimetry machine will be placed over your nose and mouth to analyze your breathing.

If used for exercise testing, you’ll wear the mask during physical activity such as running on a treadmill. This type of indirect calorimetry measures the volume of oxygen used and carbon dioxide produced during exercise. The test is performed over two 10-minute periods.

Applications of indirect calorimetry

Indirect calorimetry has many uses, including:

• Weight management
• Metabolic rate measurement
• Heart and lung disease management
• Optimization of exercise programs and nutrition

Athletes commonly use indirect calorimetry tests to improve performance without under or overexerting themselves and to optimize their training programs.

Using indirect calorimetry to personalize health strategies

Everyone’s body has different health needs. Indirect calorimetry tests can give valuable insights to your doctor so they can personalize your health strategy.

Your Aurora specialist can recommend precise daily calorie needs to meet your health goals, such as:

• Weight loss
• Weight gain
• Weight maintenance
• Improve overall health

They can also use the results to change treatments for lung and heart conditions or detect potential health issues.

The results from an indirect calorimetry test can be used as a baseline. Regular testing can highlight changes, which helps your doctor adjust treatment or nutrition plans. It can also help identify potential health issues early.