Doing your aerobics workout at any time of the day is perfectly alright, what is important is that you do them. However, majority of fitness experts and athletes believe that the best time to do aerobics training is in the early morning. They claim that fasted  aerobic burns more body fat due to the following reasons:
-When you wake up the body's glycogen stores are depleted; the body burns fat when glycogen supply is low.
-Food intake causes insulin release which in turns interferes with the mobilization of body fat. The body’s insulin levels are low in the morning, so more body fat is burned during early morning aerobics.
-There is less glucose in the bloodstream when you wake up therefore you burn more fat.
-Eating before working out means you have to burn off first what you just ate before you can tap into stored body fat and your body has to contend with elevated insulin levels after a meal.
-Doing your workout in the morning elevates the body’s metabolism rate for the rest of the day, even after the workout is over.
-Morning aerobics energizes, wakes you up and helps regulate your appetite for the rest of the day.
-It’s easier to wake up earlier to make time for your workout rather than sleeping later after a hard day at the office.

A common concern about fasted aerobics is the possibility of muscle loss. Although this is a possibility, it can only happen if you perform extreme amounts of high impact, high intensity aerobics! However, since you are tracking your progress on a weekly basis, you would immediately be aware if this were the case. If it is, then you can also immediately make the necessary modifications to your nutrition program and aerobics regimen by adjusting nutrient rations and intensity and frequency levels of workout.

The most likely causes of muscle loss are:
• Low calorie intake
• Inadequate protein
• Dieting without including a cardio/weight training program

Make sure that you develop a suitable nutritional program that includes adequate meal frequency with the correct protein carbohydrates-fats ratio and total calories, and it is highly unlikely that you will lose muscle even if you perform cardio workouts at the advanced level daily.