This is a somewhat nuanced point but I understand perfectly fine that low blood sugar or calorie restriction can cause hunger in general. No argument; you get hungry for "something."  Your body turns on the craving center of the brain, in general. 

However, what specifically you crave as a means to replenish a specific macronutrient seems far-fetched and unexplained to me.

And another one:

Food Craving Inventory

And one more, just for kicks:

Changes in Food Cravings during Low-Calorie and Very-Low-Calorie Diets

Cravings due to carbs can be both Mental and Physical.

Mental in the realm of that was good I need more.  Physical in that the excess insulin in your system will result in your body wanting more carbs to put it to use. 

For me I get both.  To control the physical I always do Carb and Protein this helps in the drop from any spike caused by the carb.

I really don't see  where did you see Cheetos in Laura post? 

due to RNY - it has been studied and documents - most of us produce too much insulin in response to food, specially carbs - even so called complex carbs. When that happens - eating carbs makes the body release too much insulin. Too much insulin will cause BS drop and cause hunger and craving for more carbs - and in that situation - quick carbs - as in simple carbs.

 I never imagined that someone could get RH from things like small qty brown rice, or sweet potatoes, or beans. I was told " as long as you eat proteins with it - you should be fine"  such a BS. The longer postop RNy I am - the stronger the reaction is. 

My body is extreme - but I do believe that most of us  post op RNY, we are much more sensitive to carbs - any carbs - than before RNY and that I see people sensitivity going up not down. 

People start reporting getting RH 1-2 or 3 years post op... when they are doing and eating the same things. Our body becomes more sensitive to carbs... 

"(...) when sugar and simple carbs are consumed, gastric bypass patients have a 20-fold increase in insulin production at six months, compared to a 4-fold increase in patients who have undergone either a sleeve gastrectomy or a duodenal switch procedure. The dramatic rise in insulin in gastric bypass patients causes a rapid drop in glucose, promoting hunger and leading to increased food consumption.(...)"

http://www.lenoxhillhospital.org/press_releases.aspx?id=2106

http://well.blogs.nytimes.com/2013/06/27/how-carbs-can-trigg er-food-cravings/?_r=0

How Carbs Can Trigger Food Cravings

 JUNE 27, 2013 12:02 AM June 27, 2013 12:02 am 525 Comments Are all calories created equal? A new study suggests that in at least one important way, they may not be.

Sugary foods and drinks, white bread and other processed carbohydrates that are known to cause abrupt spikes and falls in blood sugar appear to stimulate parts of the brain involved in hunger, craving and reward, the new research shows. The findings,published in The American Journal of Clinical Nutrition, suggest that these so-called high-glycemic foods influence the brain in a way that might drive some people to overeat.

For those who are particularly susceptible to these effects, avoiding refined carbohydrates might reduce urges and potentially help control weight, said Dr. David Ludwig, the lead author of the study and the director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital.

“This research suggests that based on their effects on brain metabolism, all calories are not alike,” he said. “Not everybody who eats processed carbohydrates develops uncontrollable food cravings. But for the person who has been struggling with weight in our modern food environment and unable to control their cravings, limiting refined carbohydrate may be a logical first step.”

Regardless of the diet they choose, most people who lose a great deal of weight have a difficult time keeping it off for good. For many people, despite their best efforts, the weight returns within six months to a year. But a few studies of weight loss maintenance, including a large one in The New England Journal of Medicine in 2010, have reported some success with diets that limit high-glycemic foods like bagels, white rice, juice and soda.

In addition to raising blood sugar, foods that are sugary and highly caloric elicit pronounced responses in distinct areas of the brain involved in reward. Earlier imaging studies have shown, for example, that the main reward and pleasure center, the nucleus accumbens, lights up more intensely for a slice of chocolate cake than for blander foods like vegetables, and the activation tends to be greater in the brains of obese people than it is in those who are lean.

But do rich desserts have a select ability to change our longer-term eating habits?

To get a better idea, Dr. Ludwig and his colleagues recruited a dozen obese men and then fed them milkshakes on two different occasions separated by several weeks. In each case, the milkshakes were nearly identical: flavored with milk and vanilla, and containing the same amount of calories, carbohydrates, protein and fat.

But on one occasion, the shakes were made with high-glycemic corn syrup; on the other, a source of low-glycemic carbohydrates was used. “These test meals were identical in appearance and tastiness, and we verified that our subjects had no preference for one or the other,” Dr. Ludwig said.

As expected, blood sugar levels rose more quickly in response to the high-glycemic milkshake. But the researchers were especially interested in what happened several hours later, about the time most people are ready for their next meal.

What they found was that four hours after drinking the high-glycemic shake, blood sugar levels had plummeted into the hypoglycemic range, the subjects reported more hunger, and brain scans showed greater activation in parts of the brain that regulate cravings, reward and addictive behaviors. Although the subject pool was small, every subject showed the same response, and the differences in blood flow to these regions of the brain between the two conditions “was quite substantial,” Dr. Ludwig said.

“Based on the strength and consistency of the response,” he added, “the likelihood that this was due to chance was less than one in a thousand.”

Previous research suggests that when blood sugar levels plummet, people have a tendency to seek out foods that can restore it quickly, and this may set up a cycle of overeating driven by high-glycemic foods, Dr. Ludwig said. “It makes sense that the brain would direct us to foods that would rescue blood sugar,” he said. “That’s a normal protective mechanism.”

Christopher Gardner, a nutrition scientist at Stanford University who was not involved in the new study, said that after decades of research but little success in fighting obesity, “it has been disappointing that the message being communicated to the American public has been boiled down to ‘eat less and exercise more.’”

“An underlying assumption of the ‘eat less’ portion of that message has been ‘a calorie is a calorie,’” he said. But the new research “sheds light on the strong plausibility that it isn’t just the amount of food we are eating, but also the type.”

Dr. Gardner said it was clear that the conventional approach of the past few decades was not working. A more helpful message than “eat less,” he said, may be “eat less refined carbohydrates and more whole foods.”

Cheetos was just an example for illustration.  My point was mainly that in order for your body to "work backwards" from "I want carbohydrates" to "craving specific foods that contain those carbohydrates" it would have to "know" what foods contain carbohydrates.  I know of no mechanism by which that cataloging takes place and I would love to learn more if it's in fact taking place and such a process would be essential to "carbs make me crave carbs" being accurate.

Thanks for the article and, indirectly, a link to that study.  I'm not at all in agreement with the author's headline and its use of "carbs" as a proxy for "high glycemic index sugar" but you can't have everything.  I would also point out that participants were drinking liquid sugar in milkshake form and that's not a food I would ever advocate for anyone.  Also, it is not in my opinion prudent to extrapolate from that experiment that relatively low-GI foods like whole fruits and intact grains illicit the same response.

But seriously, I'm always appreciative of information and discussion.

Knowing that post op RNY our body secrets up to 20 times more insulin as a response to carbs, indicates that even not very big blood sugar increase may cause a dramatic insulin response in the body causing blood sugar fluctuation.

Maybe you would be the lucky one who does not get RH post op RNY... 

RH post op RNY is one major symptoms of increase insulin response to carbs, simple or complex. 

Lord knows if you have RH then you have to manage it.  My mother is a RNY patient with the most extreme RH I've ever seen or heard of (seizure-inducing sugar crashes, etc.).

However, with all due respect, you're once again rounding up very specific claims into generalities.  Your Lenox link make the claim that RNY patients exhibited a 20-fold increase in insulin response to "sugar and simple carbs" during glucose testing, not just "carbs."  These people drank sugar water and exhibited the most extreme-of-the-extreme responses.  That's not surprising in the least and I think we should take great care applying those conclusions to minimally-processed or unprocessed whole foods.

In a nutshell the body craves carbs is because carbs is quick energy & it takes less work for the body to process it. Whether those carbs comes in the form of fruits & vegetables or Cheetos is up to you.

The body doesn't want to work at processing protein & converting that to energy because it takes more work to do that, than to process carbs. It doesn't want to work at converting the fat in your body into energy because it takes more work to do that than to process carbs.

That's why most people who eat carbs wants more carbs & it's very likely that most people aren't burning off the energy for the amount of carbs they eat, so the body turns it into fat. Basic Biology.

Interesting, Laura, because Garth now says the only thing you need to count is steps. Do 10k a day and eat clean, non-processed, whole foods. I guess times have changed:-)