Unless you've been living under a rock for the past few years, you've heard a thing or two about low-carb diets like Atkins. Founded on the principle that it's excess carbohydrates, not fat, that causes weight gain, low-carb proponents advocate restricting carbohydrate intake to as little as 20 grams per day or less, depending on the plan. According to the Food and Nutrition Board of the Institute of Medicine of the National Academies of Science, the recommended daily allowance of carbohydrates for children between ages one and eighteen is a minimum of 100 grams.

As of early 2004, both Atkins Nutritionals and Dr. Barry Sears (creator of “The Zone”) stated that they do not recommend their plans for children and only market their related diet products to adults. However, Dr. Arthur Agatston, the author of The South Beach Diet, does recommend his plan for children, as long as they omit the two-week introductory phase of the program. The same goes for Drs. Michael and Mary Dan Eades, Protein Power creators, who say that their program can be used for children as long as they start with Phase II. SugarBusters, which is less restrictive than Atkins in terms of carbohydrate allowances, has a specific plan geared towards children.

How It Works

The carbohydrates your child consumes in food are the main power source for cellular energy and central nervous system functioning. Carbs convert to glucose, and the pancreas pumps out insulin that “unlocks” cells and allows the glucose energy inside. Low-carb proponents say that consuming too many carbs overloads this finely balanced system and triggers the release of too much insulin, which is eventually stored as excess fat. Excess circulating insulin is also associated with insulin resistance and raises heart disease risk.

When dietary carbs are reduced, the body turns to the only other source of energy available for fuel — body fat. This process of burning fat for energy is known as ketosis. It can result in weight loss, although ketosis may also have some undesirable side-effects including bad breath, headaches, nausea, fatigue, and dehydration if fluid intake isn't increased. Low-carb plans usually focus on increasing dietary protein as well, which is known to promote satiety (or feelings of fullness).

Atkins and other low-carb plans replace sugars and starches with protein-rich foods, such as red meat and eggs. Critics of carb-reduction say that the high levels of artery-clogging fats and cholesterol from foods like this are a one-way ticket to heart disease. Interestingly, several studies have concluded that after six and twelve months, individuals on a reduced carbohydrate diet actually improved their blood cholesterol profiles. But there are no long-term (longer than one year) studies that measure the impact of low-carb/high-protein eating on the cardiovascular system, so the jury is still out.

Kids and Carbs

While studies have shown that low-carb eating does indeed promote faster weight loss than low-fat plans, studies specific to children, as well as long-term adult studies, are sorely lacking. And the fact is that any dietary plan that excludes or dramatically slashes a wide variety of nutrient-filled foods is not good for your child. Kids need carbs — for energy, for brain development and cognitive function, and for overall growth. The introductory phases of diet plans like Atkins and South Beach cut out or greatly restrict essential foods that kids need for nutrients, including milk and some other dairy, some fruits and veggies, and many grains (including pasta, breads, and cereals).

Is cutting your child's overall daily carb intake a bad idea? Remember the golden rule of weight management — that calories are what count. If your child is getting a lot of extra calories in the form of too many refined carbohydrates (such as from chips, fries, donuts, or sugary drinks and cereals), it makes sense to cut back. Even if those foods were not high in carbs, they aren't nutrient dense and therefore aren't great choices to begin with. Choose those carbs that have some redeeming nutritional value — like veggies, fruits, whole-wheat breads, and whole-grain pastas and cereals.

As always, speak with your child's doctor and a registered dietitian if you are interested in following a more formal program of carbohydrate reduction for your family.

Popular low-carb and reduced-carb diet plans include the following:

• Atkins. The granddaddy of all the low-carb plans, Atkins advocates an initial “induction phase,” in which daily carb consumption is 20 grams or less, and ultimately ends in “lifetime maintenance,” with a daily carb allowance between 25 and 90 grams.

• Protein Power. Similar to Atkins, Protein Power is a three-phase program that starts with a maximum of 30 daily grams of carbs and gradually increases carbohydrates to a “maintenance level.”

• South Beach. Emphasizes carbohydrate quality over quantity, encouraging a variety of low-glycemic carbohydrates.

• SugarBusters. The only one of the reduced-carb plans that has a program geared towards children, SugarBusters recommends that kids have a daily mix of 50 percent carbs (primarily from high-fiber sources), 30 percent fat, and 20 percent protein. It also focuses on reducing sugar in the diet.

• The Zone. Being in “The Zone” refers to keeping insulin levels in balance through a low-glycemic load diet that derives 35 to 45 percent of daily calories from carbohydrates (based on an 1,100 or 1,400 calorie daily diet for women and men, respectively).

The Glycemic Index

The last three of these plans — SugarBusters, South Beach, and The Zone — are based on the concept of choosing the “right” types of carbohydrates, those with a low glycemic index and/or glycemic load. ( SugarBusters calls it “insulin response.”) The glycemic index is a measurement of how quickly the carbohydrates in specific foods raise blood sugar levels (and subsequently, insulin levels) on a scale of 0 to 100. Foods with a high glycemic index (over 70), or GI ranking, will trigger a quick spike in blood glucose levels, while low-GI foods (under 55) cause a slow and steady rise.

The GI has several limitations. First of all, not all foods have a glycemic index rating. The laboratory procedure for assessing the GI of a food is time-consuming and expensive, and only a few facilities in the world have the proper equipment and protocols in place to do the testing correctly. Second, the GI by itself doesn't give you the whole picture. Some foods may have a high GI but contain relatively little carbohydrate to begin with. A second tool, known as the glycemic load (GL), is a measurement of the GI of a food multiplied by the grams of available carbohydrate (carbohydrate minus fiber content) found in one serving. A GL of ten or less is considered low.

While the concepts of glycemic load and glycemic index can be helpful in food selection and are extremely useful for individuals trying to establish dietary control of diabetes, they are probably way too complex for your child to use on a daily basis. In fact, they can even be overly complicated for the math-challenged adult. Learning more about those whole foods that provide the best nutritional bang for the buck is probably a better use of your time and effort. Generally speaking, whole unrefined and unprocessed foods that are high in fiber, such as broccoli, strawberries, and whole-grain cereals, will have a low GL anyway.