Energy balance

Doubly labelled water (DLW) is the most accurate method for measuring total daily energy expenditure in free-living subjects, providing an error of less than 7-8% over 7-21 days, whereas chamber-based systems are more accurate for long-term measurements but fail to reflect real-life behaviors due to confinement constraints.

For accurate assessment of total daily energy expenditure in real-world settings, doubly labelled water is the gold standard. However, it is expensive and does not break down energy use by activity type, so it is primarily used in research rather than clinical practice.