For body fat percentage, there are simple methods to do this, even using the scale, but then it depends if you're a male or female and IIRC, they measure various points of your body, like waist, hips, thighs, arms in women or the pinch test.
You can also use a BOD POD (air-displacement plethysmography). It's about 50 pounds in the UK and it gives you the proportion of total fat mass and lean body mass which is overall your body composition. As far as I know, a lot of athletes use one, especially when there's a need to see how you're responding to your training regimen (it's used by regular people, especially when in need of a proper diet).
Then there's the DEXA thing or iDXA. The US olympic's team has this. They do a full body scan (it's x-rays) and then it spits out highly accurate numbers on total body fat, lean body mass, bone density, images of tissues, and this thing gives you regional compositions (so different body parts). I guess he probably did this at some point, as an elite athlete.
I remember Michael Jordan's body fat was measured at 4% and this was considered extremely low therefore often mentioned. Honestly, I am not sure about the 2% because that sounds way too low for me (and I've heard of instances of this causing problems with muscles) but he is very slim, due to his body type so who knows. I definitely wouldn't be surprised if they low-balled that a bit, and it's actually around 4% but even if that's the case, that's still pretty much on the bottom limit.
.So If Yuzuru only has 2-3 %, then it's incredible. Maybe someone with medicine studies can explain this things.
Longevity and health are all I wish for.
. Evgenia will never wash her face againnot like we didn't all know already
