Wearables can't measure energy expenditure, at most they give you an overblown estimate that is only weakly correlated with actual expenditure. The closest thi

Wearables can't measure energy expenditure, at most they give you an overblown estimate that is only weakly correlated with actual expenditure. The closest thing to measuring expenditure is a power meter on a bike or ergo, and then you still technically have to do a lab test measuring expired gases from your breathing to estimate efficiency.