Our caveman ancestors had an inbuilt urge to eat foods with a sugary taste, as sugar is a ready source of energy which was valuable to their survival. Eating sugar made them feel pleasure by stimulating the release of a chemical called serotonin, and probably other mood-enhancing substances as well.
This survival instinct is still part of our genetic makeup today. The trouble is that these days, we eat far more sugar than our ancestors ever could. They could only eat sugar sporadically, in the form of honey, berries and other fruits and roots when they came across them. Not only are these sources of sugar constantly available to us, but we also have highly refined and concentrated forms of them which give us a sugar 'hit' that our ancestors would never have got.
When we eat large quantities of sugar today (and other carbohydrate foods such as flour, bread, rice, potatoes and fruit which break down into sugar in the process of digestion), our blood sugar shoots up high. This triggers our pancreas to release far too much insulin. (Insulin is the hormone which controls whether the sugar is burned off as energy or turned into fat for storage in our fat cells.)
The sugar hit and the exaggerated insulin response makes our blood sugar level go too low. This signals to our brain that we need to replenish the blood sugar, and so we feel hungry again. In this way, our blood sugar/insulin control mechanism becomes imbalanced.
This imbalance not only makes us feel hungry, it causes us to lose the effect of the 'feel-good' chemical serotonin, and possibly other hormones such as leptin which tell us when we are full. So we eat more in an attempt to both feel better and to stop our hunger, and so the cycle goes on.
This is how sugar and carbohydrate cravings begin, and the only way to stop them is to cut down or eliminate the sugar and other refined carbohydrates from our diet. A low GI diet may help, but for many people who have an exaggerated response to carbohydrates of any type, the best solution is a very low carb diet such as the Atkins Diet.
Sugar cravings and carbohydrate cravings can also be caused by food sensitivities and candida or yeast overgrowth. In this case, it may be necessary to go on a no sugar, no yeast diet and/or eliminate the foods to which we are individually sensitive before we can eliminate the sugar or carbohydrate cravings.
Artificial sweeteners, although not sugar, are also thought in some people to cause an insulin surge, or at least to confuse the brain into sending 'eat more' messages.
Kids are particularly prone to sugar cravings if they eat a diet full of sugary drinks and fast foods because these give them a constant sugar hit which amounts almost to an addiction.
An addiction to sugar or carbohydrates can only be broken by eliminating the culprit foods entirely for a period of time. After eliminating sugar and other refined carbohydrates from the diet for a couple of months or so, you lose the sugar or carbohydrate cravings. Your taste buds also become more sensitive and a much smaller amount of the food in question is needed to taste sweet.
More about the connection between diets high in sugar and refined carbohydrates and sugar or carbohydrate cravings can be found in the ebook "Why Can't I Lose Weight".
If you or your kid have sugar or carbohydrate cravings, the best solution is to follow a low carb or low GI or low GL diet. The "Easy Guide to Low Carb, Low GI & Low GL Diets" explains what the differences are between these diets and how to do them.
The recipes in the "Low Carb / Low GI Cookbook" are all sugar free and low in carbohydrates so they are particularly suitable for anyone with sugar or carbohydrate cravings.