For people tracking weight-loss goals, an Apple Watch can provide an estimate of calories burned. The figure is not exact: the watch uses heart-rate readings, personal metrics, movement sensors and GPS, and its accuracy depends in part on how it is worn and configured.
First, wear the watch snugly but not tightly, with its heart-rate sensor flush against the skin. It should sit above the wrist bone and remain in place rather than rotating as you move.
Second, check that your personal information is up to date, particularly as your weight changes. Calibration can also help. On the paired iPhone, turn on Motion Calibration & Distance under Location Services and System Services. Then take a 20-minute walk at your usual pace on flat ground with a clear view of the sky while wearing the watch. Heavy tree cover and tall buildings can affect GPS reception.
Third, select the workout mode that best matches your activity. Apple Watch uses different algorithms for different movement patterns, so choosing a relevant mode can affect the calorie estimate. For instance, the source article reports a higher average calorie figure when using High-Intensity Interval Training mode for HIIT sessions than when using Functional Strength Training mode.
Even with these adjustments, the watch cannot provide a definitive measurement of total energy expenditure. The article recommends speaking with a physician for personalized weight-loss advice and emphasizes a balanced diet, regular movement and overall health.
Sources: Tom's Guide.