and tell me why you'd lose muscle if you don't re-carb, please.

Let's see why that is so important!
In normal conditions the skeletal muscle glycogen concentration ranges from 1.5 grams to 2 grams per 100 grams of skeletal muscle tissue. A Swedish researcher BERGSTROM (1969) has shown that after a low carbohydrate diet that lasts for a period of 3 days accompanied with prolonged physical exercises/efforts one's skeletal muscle glycogen depots fall to a concentration of about 0.6 grams! After this limited 3 day period of carbohydrate depletion, a carbohydrate-rich diet was followed causing a new higher level of muscle glycogen content.
If the "depleting glycogen phase" has been done correctly, inducing a dramatic lowering of glycogen depots, it creates a "hunger state" for your muscles so that during the next "super compensation" phase they will store more glycogen than in normal conditions. In other words, they could store from 3.5 grams of glycogen to even 4 grams per 100 grams of skeletal muscle tissue. Don't forget that 1 gram of glycogen is linked with 2.7 grams of water. This means that if a bodybuilder has 45 kg (99 pounds) of Lean Muscular Tissue, (don't confuse Lean Muscular Tissue with Fat Free Mass; Lean muscular tissue is in other words "MUSCLE", instead Fat Free Mass consists of Lean Muscular Tissue + Bones + Water) he can increase his bodyweight about 4.86 kg (10.69 pounds) with glycogen and water during the carbohydrate loading phase.
The calculation goes like this:
1) Kg 45 x 10 = 450 hg
(Kg of skeletal muscle converted into hg; 1 kg equal 1000grams, 1 hg equal 100grams)
2) hg 450 x 4 = 1800 grams (total muscular glycogen content)
(the number 4 stands for the maximum glycogen content per 100 grams of muscle tissue)
3) 1800 grams x 2.7 = 4860 grams (final bodyweight achieved)
(2.7 is the grams of water linked to 1 gram of glycogen)
All this weight gained comes from glycogen and water. It's not water retention! Water retention means that water is being kept between the cells (in this case between the muscle cells) giving the muscles that smooth look that won't give you that ripped look that is so hard to reach after all the sacrifices that you made while preparing for competition. The water gained is all carried into the muscle cells because glycogen depots are located only inside and not outside the muscle and liver cells. That's why this loading phase makes the muscles appear bigger and fuller!
To cause this "supercompensation" it is very important to reload the right amount of carbs. The consumption of fewer carbohydrates than those needed won't lead to the desired effect and you may even notice that your muscles feel empty and become smaller. This is what usually happens to competitive bodybuilders! If this does happen, it would have been better NOT to have done the "depleting carb phase" at all.
If the consumption of carbs exceeds the amount needed to refill all your glycogen depots completely, that surplus will be converted into subcutaneous bodyfat. NOT GOOD.
Now you probably want to know how many carbs you should be eating in order to refill all your glycogen depots while avoiding the risk of reducing your muscle size or gaining bodyfat.
The recommended carbs consumption has been estimated at 400 to 600 grams per day for a period of 3 days after the depleting phase. There are also other very reliable experts on bodybuilding that instead of suggesting the 3 day depleting formula, they opt for 2 days for depleting and 2 days for reloading. My opinion on this is that the difference between the number of days for depleting and reloading is strictly personal and not applicable to everybody; and this is for many different reasons. Even the good results obtained with different schedules on different individuals cannot be simply applied directly to everyone else.
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