These devices measure the concentration of CO2 and O2 in exhaled breath to estimate the Respiratory Exchange Ratio (RER). An RER close to 0.7 suggests fat oxidation, while a value near 1.0 indicates carbohydrate oxidation. The goal is to use this data to improve metabolic flexibility—the body's ability to efficiently switch between fuel sources, a key aspect of metabolic health and healthspan.
Verdict
A potentially useful tool for bio-feedback, but not a direct intervention.
HEALTHSPAN IMPACT
Experimental
RISK LEVEL
Very Low
EVIDENCE GRADE
B
MONTHLY COST
$200 - $600
Protocol
- Users typically breathe into the device upon waking to establish a fasted baseline metabolic state.
- Measurements are often taken before and after meals or exercise to assess metabolic response.
- Data is tracked over time via a companion app to observe trends in metabolic flexibility.
Flags
- Accuracy can be affected by recent meals, exercise, alcohol, and breathing patterns.
- Device accuracy may vary and is not a substitute for clinical metabolic testing.
- Focusing excessively on a single metric may encourage disordered eating patterns.
- Data is a lagging indicator of metabolic state and should be interpreted as a trend.