Cortisol is antagonistic to testosterone – when cortisol is high, testosterone automatically goes low.
With frequently high level of cortisol your muscle growth slows down, at least for two reasons.
1) Low testosterone = slow muscle growth.
2) Elevated cortisol breaks muscles down (eats them away).
And contrary to the general opinion, the burning of excess fat is actually slowed down. Popular opinion is that the best method of fat loss or burning fat is torture by prolonged jogging and long workouts. This is erroneous. During the workout you burn less fat than AFTER THE WORKOUT. After a proper workout the hormones are at the levels necessary to burn fat. It is the same as the fact that muscles are not built during the workout, but after it.
That’s why a good training program is needed which contains these principles.
You grow while you sleep, you burn fat while you sleep
These two things – burning fat and muscle growth, take place mainly during SLEEP. You lose fat while you sleep, as then the fat-burning and muscle-building hormones are most active.
The best sleep time is from 10/11 PM to 06/07 AM. In any case, eight hours at least.
Also with proper diet i.e. proper hormonal reactions, your body will be in a state of fat-burning 24 hours a day as it will be getting its energy from fats. Whether body fats or dietary fats, that is regulated by eating proper amount of fats, protein and carbs.