If you follow a lot of fitness enthusiasts on social media, you often see a lot of people post “calories burned” snapshots from their workout tracking device app. You will also see some people ask things like “I’m burning 1000 calories, but not losing weight…”
One word of caution on these devices: Almost all energy tracking devices dramatically overestimate the amount of energy expended (calories burned) for physical activity. https://bjsm.bmj.com/…/09/07/bjsports-2018-099643.full.
One study showed the devices overestimated calories burned by 27.5% to 93%.
Generally, they do measure heart rate well, but they grossly overestimate calories burned. Their usefulness is just limited to comparing relative intensity – i.e. if it said you burned 500 calories in one workout and the next day you burned 500 again, you can assume you are maintaining intensity. But that is about all you can assume with these.
If you are using these to track calories and it says you burned 1000 calories, but you really burned only 500 calories, and you are eating factoring in 1000 calories expended, well…