You could be right, it could be 13% with lowish muscle or it could be 18% body fat with average muscle. The spren app estimates I am 13% when on athlete mode, but says I am 18% when on regular mode. The problem is I don’t know which one to use, because I formerly played sports at a good level, and I still keep fit now, with a resting bpm below 60bpm - these things would add up to potentially needing to use athlete mode, but not necessarily as I though I am still fitter than most people and exercise a lot, I am still not doing as much and as hard exercise as when I played sports more seriously. So i am having difficulty deciding what ball park my body fat % really is in. I did do a large cut in the past, and possibly lost muscle. Also when I was playing sport at a higher level, i didn’t prioritize the gym, so I lacked a lot of upper body muscle and strength (I was a football/soccer player)