Are smart watches accurate at measuring body composition?

[404040]

Just got it to tell me my skeletal muscle mass, bodyfat percentage etc. Apparently it sends microcurrents through your body or some shit and it can get all that information.
Is this accurate at all? I tried doing it a few times and I got slightly different results each time, but it was around the same.

 

[Orc]

they're not accurate for measuring your initial stats but they're fairly good for tracking progress, i.e they won't give you an accurate bodyfat percentage but it will still go up and down as you lose or gain weight.

 

[404040]

they're not accurate for measuring your initial stats but they're fairly good for tracking progress, i.e they won't give you an accurate bodyfat percentage but it will still go up and down as you lose or gain weight.

do you know if they usually underestimate or overestimate?

 

[Orc]

do you know if they usually underestimate or overestimate?

underestimate, makes people think they're way leaner than they actually are.