Because, at his height/current build he'd either have to put on some serious muscle mass, or weight like 130 pounds. And no man, regardless of height should be that scrawny. It's not going to be beneficial to his health or performance.

15% is super easy to maintain, even for someone who previously had weight issues. 10% requires a bit of calorie restriction to stay that lean. If he were competing it'd be one thing. For living and being healthy it's pushing it.


To the OP, I'd dial back the cardio slightly and do a bit more weight training. Finding a solid lifting program would be ideal, and just doing some light cardio or interval on your "off" days. If you want to improve your bodyfat percentage, you need to gain some muscle, instead of just wasting away so put a little more focus on the weights. A more realistic setup would be something like:
M: Lifting
T:Cardio (low intensity longer session)
W:Lifting
Thurs: Cardio/Intervals
Friday: Lifting
Saturday: Bike
Sunday: off/easy ride

Obviouisly you could ride your bike instead of doing any of the cardio workouts. But feeling like you have to run and lift every single day isn't productive. Less is more in some cases.