In today’s world, many people believe that carbohydrates are bad. It is a big misconception that actually limits their results. It’s not exactly hard to understand why these misconceptions and misunderstandings exist though because over the last few decades Net Carbohydrate or Impact Carbs came about because of the popularity associated with eating a diet lower in carbohydrates.
For starters, it needs to be made clear that carbohydrates are critically important for exercising individuals, particularly for those folks wanting to perform at high levels or to increase their performance. Carbohydrates are a high octane fuel that your muscles can utilize very quickly and efficiently to produce energy. It is actually your bodies preferred and primary fuel source.
Unfortunately, our body has a limited ability to store carbohydrates which can become problematic for people trying to perform maximally but also maintain a diet that provides less than ideal amounts of carbohydrates. For these reasons, many major organizations such as the U.S. Department of Health and Human Services or the U.S. Department of Agriculture and American Dietetic Association recommend that people consume a diet that contains around 45 to 65 percent carbohydrates along with a minimum recommendation to consume at least 130 grams of carbohydrates each day. Again speaking from a performance perspective, some sport nutrition experts suggest that performance gains are hard pressed to occur if the diet contains less than 40 percent carbohydrates.
The glycemic index of a carbohydrate refers to the impact of different carbohydrate-rich foods and fluids on changes in glucose and insulin. In this respect, the glycemic index ranks foods from 0 to 100 with values less than 30 to 40 being considered ‘low glycemic’, 40 to 70 ‘moderate glycemic’ and anything greater than 70 considered ‘high glycemic’. Low glycemic index foods raise blood glucose and insulin levels more slowly than higher glycemic index foods. A number of scientific reports have suggested the magnitude of increase of glucose levels, the rate at which this increase in glucose occurs and the overall insulin response to food ingestion, all increase the risk for obesity, cardiovascular disease, hypertension, etc. One additional problem is the common occurrence that many high glycemic index foods are also high in fat and make their overall caloric levels quite high. Add in the fact that these foods also taste really good and are oftentimes consumed in social settings result in a situation where calorie intake can get out of hand in a hurry. As such, foods are often categorized as high, moderate or low glycemic index foods, which can be found in the table after the article.
Glycemic index can also be influenced by some other factors. For example, foods which contain larger particles overall take longer to fully digest and more often than not have lower glycemic index values. Using oatmeal as an example. Instant oatmeal is more ground up to allow for it to “cook” faster with the hot water that’s added when compared to regular oatmeal or even steel cut oats.
A food’s fiber content will change digestion and glycemic outcomes as well. Soluble fibers (e.g., oats, barley, beans) take longer to digest when compared to insoluble fibers that merely pass through the digestive system. Higher acidity foods or fluids such as fruit, vinegar, or pickled foods take longer to digest because the body has to first neutralize the acid content before completing the digestive process. Like fiber content, fat content impacts digestive time and resulting glycemic index values of the foods or meals consumed. For individuals focused upon weight loss, losing fat and improving body composition, low to moderate glycemic index foods are recommended as they effectively keep large increases of the hormone insulin from occurring, which has a powerful ability to store fat throughout the body. Alternatively, individuals focused upon performance should consider high-glycemic foods at predetermined times. In this respect, higher glycemic index foods are advised for consumption prior to a workout or competition because of its ability to rapidly digest and provide valuable glucose (a carbohydrate) for fuel.
Similarly, high glycemic index foods are recommended after an exhaustive exercise session, especially if another exercise bout will begin in only a few hours, because they have been shown to promote a faster rebuilding of lost muscle glycogen. For the misinformed individual shooting for weight loss, this creates a situation where foods such as fruit, yogurt, whole grain breads, etc. that may contain high glycemic foods are avoided when in actuality these foods also contain valuable sources of protein, fiber, vitamins/minerals and other important nutrients. While not a universal rule, it’s safe to say that a food which contains primarily high glycemic carbohydrates, a good amount of fat and/or doesn’t have an appreciable amount of vitamins or minerals within it should be consumed in limited amounts. On the flip side, if a food contains high glycemic carbohydrates but also has a good amount of fiber, vitamins, minerals or other nutrients; this is a food which should be consumed without concern of its impact on your ability to lose weight or fat and improve your body composition.
The low carbohydrate craze that swept across the country like a cold front from the North brought with it a number of marketing approaches that were employed to convince the consumer the foods they were consuming did not have carbohydrate value. One common misconception with these types of foods is that because they are low in carbohydrates they are low in calories, which may not always be the case.
Much like a food that is labeled “low fat”, if the food manufacturer replaces the fat or carbohydrate with something else which raises the caloric value of the food, consuming this food (like any other) in excessive amounts will result in weight gain. If you’ve ever seen a low-carbohydrate bar or food that highlights “Impact Carbs” or “Net Effective Carbohydrates,” the foods likely contain a number of sugar alcohols or glycerine. Common sugar alcohols used are maltitol, isomalt, mannitol, sorbitol, xylitol, or lactitol. These food components are used primarily for two reasons; because they may not contribute as many calories per gram or they have little impact on glucose and insulin changes. The sugar alcohols listed range in caloric values between 0.2 and 2.6 calories per gram. When compared to the traditional four calories per gram often considered for carbohydrates, the caloric density of sugar alcohols is lower, however, if the manufacturer puts more of them in the product to provide an equal taste then you haven’t made any headway. The bottom line here is that total carbohydrate content or caloric contents still predominates.
Finally, for those interested in calculating for themselves, net carbohydrates (in grams) = total carbohydrates (in grams) – fiber content (in grams) – sugar alcohols (in grams) – glycerine (in grams). Glycerine is particularly problematic because it has a relatively high calorie density for a carbohydrate at 4.32 calories per gram, but it is used a good bit because it has very little impact on glucose and insulin levels. So companies end up marketing something to suggest it is favorable to your health (reduced glycemic impact), but in the end likely has just as many calories as other non-carbohydrate equivalents. It is also worth noting that companies aren’t required by law to tell you how much of it is in the food you are consuming.
In summary, carbohydrates are critically important, particularly for those people who regularly exercise and strive to increase their performance. While foods which highlight net carbohydrates or impact carbohydrates need to be interpreted with a good deal of caution, glycemic index is something people can use to help sustain their energy levels and recovery from exercise. Overall, a diet containing nutrient-dense foods with low to moderate glycemic index carbohydrates should be considered on a regular basis throughout the day. When times require you need a fast delivery of carbohydrate, such as before a workout or in recovery from a workout, a high glycemic index carbohydrate should be considered due to their ability to digest quickly and rapidly replace the depleted fuel stores throughout the body.
Click on the chart below to enlarge and print it.