See if you're fat...
Calculate your body mass index
That BMI is a bit rough.
According to that, if I lost 10kgs I'd still be in the very highest/borderline range for the 'OK' range.
I have put on a few kilos lately due to poor diet and a full work/study workload, but if I lost 10kg without losing much muscle, I would be
ripped.
That's hardly what I would consider an indicator of healthy body mass.
As it is, I'm just drying off after a shower after 1-hour cardio/weights workout, so those 10kgs shouldn't be an issue for long.