Fast Carbs, Slow Carbs & Protein Diets

First it was low versus high carbs, now carbs have developed speed in two modes: fast and slow. Conflicting dieting advice and research adds to dieters' confusion and nutrition labels don't always help. Packaging claims aren't regulated and many people neglect to look at the label. According to a 2005 AC Nielsen global survey involving 21,261 people, only 21 percent check nutrition labels regularly. Fast carbs, slow carbs and protein provide additional confusion to the nutrition label. Understanding the concepts behind the glycemic index will help sort the confusion and allow you to make informed decisions.

Energy

There are three energy sources, or macronutrients, the body can use: carbohydrates, fats and proteins. These are made of different molecular structures that require varying degrees of processing before they can be used as energy. Carbohydrates are processed quickly and are the body's primary energy source, preserving fats for back-up energy and protein to build and maintain muscles. Fat is utilized as the secondary source of energy when high-energy output is not needed or when carbohydrates are unavailable. Proteins are rarely used as energy because they are needed to build cells for body tissues, such as muscle and skin. The glycemic index rates carbohydrates "fast" or "slow."

Glycemic Index

The glycemic index is a scale from 0 to 100 that ranks carbohydrates according to their effect on the body's blood sugar level. Slow carbs are under 55, and include beans, lentils and grapefruit; fast carbs are over 70, such as potatoes. Slow carbs don't raise blood sugar, while fast carbs can spike it; each process carries benefits and drawbacks.

Fast Carbohydrates

Fast carbohydrates are processed quickly and tend to be lower in fiber and higher in calories than slow carbs. Fast carbs are generally simple carbohydrates containing one sugar molecule, or monosaccharide. Fast carbohydrate foods include white bread, chips, soda and candy. Fruit is a simple carbohydrate containing a one sugar molecule, called fructose, but fruit is also rich in fiber, vitamins and minerals. Due to the fructose, however, fruits are high on the glycemic index and considered fast carbs. There are always exceptions to rules, some complex carbs, such as potatoes, are considered "fast" because the starch causes a spike in blood sugar. There are times when fast carbs are desirable, such as low blood sugar levels, or after high-intensity exercise, when glucose is needed for muscles, cells and organs quickly.

Slow Carbohydrates

The theory is that slow carbs take longer to absorb, keeping you full longer without flooding the bloodstream with glucose. It is also hypothesized that the body will use, or oxidize, more stored fat when eating slow carbs since less glucose is available. Slow carbs are typically complex sugar molecules, called polysaccharides, containing fiber, vitamins and minerals. These carbs take longer to digest preventing a rush of glucose immediately after a meal. Examples of these carbs include lentils, black beans, soy beans, skim milk, lean protein, cottage cheese, non-starchy vegetables.

Protein

Lean protein is recommended for GI diets because these foods take longer to digest and keep you full longer. Tim Ferris, author of the "4-Hour Body," states that protein has a higher thermogenic effect, meaning digesting protein requires more energy, which increases metabolism and burns more calories as "heat." Proteins also adds essential amino acids and many vitamins you cannot get from vegetables or beans, with the exception of soy, which is a complete protein.