Thread: problem with aerobics.

hello,

I'm 22 years old, 15.3% BF , 65.5KG weight, 1.71 height, target: gain mass , about 5 months in gym.
2 months ago i didn't any aerobics and i gain 1.5KG in fat mass in addition to 700gram muscle mass and 14.2% BF (before that i was 12% BF)
in the last month, i did 3 times a week hard aerobics in heart rate 170-180, 2 hours before aerobics i ate meal contains 25g protein + 50g carbs and unsaturated fat, 45mins aerobics exercise and again 25g protein+50 carbs and unsaturated fat (about 10g)
today i check my weight and i got this: 15.3% BF, and just 100g of muscle mass
my coach told me the problem is because i did hard aerobics and i have to do aerobics in 140 heart rate (it's 70% from my max. heart rate) about 45mins.

i really don't know what to do, if this is the situation in 3 months i'll have to burn fat and because of that burn muscle. please help me

Thats like a little over 5 foot..5'1"/5'2"