When should you eat your carbs?

If your goal is to keep off body fat, retain lean muscle mass, and look good while doing it then:

Try sticking to vegetables and fruits (low glycemic - not blood sugar and insulin spiking) throughout the day for your sources of carbohydrates.

In the period of time right before or after a training session or physical activity that calls for more high intensity efforts, then you're allowed to have more starchy carbohydrates.

Higher intensity (moving/lifting quickly and even with large loads/weights) efforts require your body to use carbohydrates for fuel. So it would be important to consume more starchy carbohydrates prior to, or after your high intensity session(s) to replenish the muscle glycogen, as well as liver glycogen that were burned for energy.

Starchy carbohydrates "...include bread, pasta, rice, couscous, potatoes, breakfast cereals, oats and other grains like rye and barley." Source

Higher intensity efforts do not include long distance runs, cycling, rowing, etc. where your pace is slower than the elite athletes performing those same activities, finishing near or at world record speeds.

For example, if the fastest Marathon finish time is right over 2 hours, then your Marathon finishing time at 4 hours shouldn't warrant you to eat such a large load of starchy carbohydrates prior to, and after the event...

...if your goal is to keep off body fat and retain lean muscle mass.

This is the case since when we're at rest and even performing lower intensity efforts, we're using primarily using fat for fuel.

Again, if your goal is to keep off body fat and retain lean muscle mass, then your goal is to eat lower glycemic carbohydrates throughout the day, to spur your body's ability to use fat for fuel primarily. 

Then around your intense training or activity, you're allowed more higher glycemic (blood sugar and insulin spiking), starchy carbohydrates.

So the lesson is Carb Up...for Intensity!