Oura and Calorie Burn
One of the more interesting features of the Oura Ring beyond the tracking of sleep and readiness is the tracking of active and total calorie burn. Oura undertook over a year of development and lab testing to produce a calorie burn which is 85-90% accurate as compared to an indirect calorimeter.
Some background on how calorie burn is calculated is outlined below.
Basal Metabolic Rate
BMR is the amount of energy your body expends over 24 hours and while at rest. This can be thought of as your base calorie burn.
The Total Burn field in the app will show your BMR when you first wake up in the morning. This field is reset at 4am each day and is your projected BMR for the day. Your BMR is estimated from your age, gender and body weight using the well known Schofield formula.
Why is the Oura Activity Measurement More Accurate Than You Might Think!
Comments about inaccuracy or imperfect Oura activity measurements are typically based on the following:
- Many people compare Oura calorie expenditure to other devices they trust (Fitbit, Apple, etc) and not calibrated scientific measurements (Indirect Calorimeter, Double Labeled Water). Many wearables significantly underestimate the energy expenditure of household activities, while they overestimate the workload in walking and jogging.
Reference: NELSON, M. B., L. A. KAMINSKY, D. C. DICKIN, and A. H. K. MONTOYE. Validity of Consumer-Based Physical Activity Monitors
- Accelerometers typically underestimate certain sports (including strength training, cycling, etc). Despite this, the error amount is a small fraction of a typical person’s Total Burn as calculated by Oura – unless your day includes several hours of these activities.
- Some believe the tracking of Heart Rate (HR) during exercise guarantees an accurate estimate of the calorie burn. This is not the case. HR based calories are only accurate if you know your fitness level and maximal heart rate. Serious athletes might know these, but it is less likely for general fitness enthusiasts. Furthermore, HR based calories are overestimated when an activity is performed in the heat or for activities of longer duration. This is due to what is known as HR drift, wherein your HR starts to increase despite the same energy output.
The bottom line is that the Total Burn (Energy Expenditure) presented by Oura will on average be within 80-90% of the accuracy of calibrated scientific equipment. You can feel confident that the calorie burn presented can be relied on for weight and health management.