Very real as most low-carbers who are honest about their struggles will reveal. If there are some carbs you have consumed recently, cravings for more can come and bite one in the you know where at any time of the day - even after a substantial low-carb meal! Sometimes that craving is so great that one succumbs. Now that is not the end of the world - enjoy whatever it is if you must - and get back to a strict LC meal soonest possible. Having tasted the naughty no-no sometimes gives us back our resolve to get back on track, because of the undesirable side effects and sometimes simply because the craving is satisfied and that is the end of that. For me, it's not salty things like chips I crave when I've had carbs creep into my diet - it is sweet things. That is why it is actually not such a bad idea for me to have something baked in the freezer or a frozen candy treat or whatever for just such an occasion.
Cravings are sometimes super-strong and it is an iron will that is required to say, "No!" Giving in means losing the edge on weight loss for a day or two or more, but never ever give up or have a defeatist attitude, where now you have failed and in your mind, therefore, can have free license to eat carbs every meal every day until all the weight you have lost is back again. This kind of attitude is very, very common, but so self-destructive. Love yourself much more than that! Find some carby-tasting replacements to satisfy those cravings and then stick with your WOE. Your body will thank you and later your mind will too when you feel and look fantastic!
How long before the cravings subside? Basically it takes about 3 days on a strict low-carb diet for the carbs to be out of your system and for the cravings to subside.
Here are people confessing their Carb Sins.
Chromium and L-glutamine can help with bad cravings for carbohydrates.