The Study
Training-induced changes in daily energy expenditure: Methodological evaluation using wrist-worn accelerometer, heart rate monitor, and doubly labeled water technique
This study tested if a fitness tracker can tell if someone burns more calories after starting to work out. It compared the tracker’s numbers to a super accurate method used in labs. It found the tracker was pretty good at spotting the increase — but only in young men who were already somewhat active. It doesn’t prove the tracker works for everyone.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
When you start exercising, your body burns more calories — even when you're resting — because you gain muscle. But most fitness watches don't notice this unless they know your muscle mass.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 560 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — this means your watch might think you're burning fewer calories than you actually are, especially if you're building muscle.
- 2Correcting for muscle mass makes the numbers much more accurate.
- 3After 12 weeks of training: 1) Total calories burned went up by 1.13 MJ/day (like eating 270 extra calories).
- 42) Fitness watches alone missed half of that increase.
- 53) Adding heart rate data during workouts fixed most of the error.
- 64) Muscle gain added 0.18 MJ/day (43 extra calories) to resting burn — only visible when using muscle mass, not weight, to calculate baseline.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
PLoS ONE
Year
2019
Authors
H. Kinnunen, K. Häkkinen, M. Schumann, L. Karavirta, K. Westerterp, H. Kyröläinen
Related Content
Claims (6)
People who engage in physical exercise burn about 5% more energy per day than those who do not.
In healthy young men doing endurance and strength training, using both wrist motion sensors and intermittent heart rate measurements provides a 15–20% more accurate estimate of daily energy expenditure than motion sensors alone.
Using fat-free mass rather than total body weight and age in energy expenditure calculations removes a consistent overestimation error in measurements taken by wrist-worn motion sensors in people doing resistance training.
After 12 weeks of combined endurance and strength training, healthy young men experience an increase in resting energy expenditure of 0.18 MJ/day due to gains in fat-free mass; this increase cannot be detected if baseline metabolism is estimated using only body weight and age.
In healthy young men, a 12-week program of combined endurance and strength training raises total daily energy expenditure by about 1.13 megajoules per day, primarily due to increased resting energy expenditure from added fat-free mass.
In healthy young men, wrist-worn motion sensors measure activity-induced energy expenditure during resistance and endurance training at about half the level detected by doubly labeled water measurements.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.