You should do your aerobibs first thing in the morning before eating
breakfast, since at this point your muscles glycogen stores are
depleted and thus your body is forced to use stored fat as energy!
Furthermore, your metabolic rate can stay elevated for as long as 18
hours, provided you do not go to sleep! So, there are the two very good
reasons to do your aerobis in the morning.
Aerobics should be vigorous, or even interval type strenuous training.
Admittedly, this type of rigorous training does use mainly glycogen
(carbs) as energy (if available), but after the workaout it uses a lot
more fat than does less demanding aerobic exercise! So, the total fat
use is probably even higher! And, it uses much more energy per time
than less demanding aerobic exercise, so at least those carbs have no
wya of being stored as fat since they are used. So, to use an egual
amount of calories (fat and carbs), do you want to do aerobics for an
hour or 20 minutes? The choise is yours! And with this kind of intense
interwal training you will have a much better cardiovascular condition,
which means you can train harder at the gym as well!
As for carbs, consume most of your daily carbs at breakfast and lunch
and make sure they are of the slow and fibrous kind! Do not consume any
carbs after 8pm, unless you have been weight training that evening! In
that case, all the carbs will likely be used to replenish used muscle
glycogen stores. This is good!
Caution! Vigorous aerobics might affect muscle gains negatively,
specifically in the muscles that are used for that aerobics (usually
lower body, that is).
A good and effective workout could be to take a light barbell and do
deep squats, power cleans (end jerks) and barbell rows a few long (20
reps) sets back to bac without any pause ien between! The more muscle
mass you use, the more calories you burn and the more you elevate your
metabolic rate (which stays elevated for quite some time)!