Consistent energy deficit and high protein intake. I still believe fasted training (with protein intake prior to the run to maintain lean mass) can oxidise fat.
He is just entering his teenager years where growth becomes important and injury risks are high. I would start with body weight exercises with him rather than weights.
You can increase your muscle mass as well as reducing your fat. Its tough but possible! Nutrition should be on point. Try to hit approximately 2 of protein per kg BW per day, and aim for an energy...
How did you measure your bodyfat? DEXA method will be the gold standard method to measure your BF%. I agree, if you were 15% and do not see any muscle mass definition, thats a clear explanation that...
I will recommend you are honest, and you explain how you feeling with your coach. Indeed ask for why you doing certain things! Coaches should make sure their plans are evidence-based and not...