Nutrition

June 8, 2010

The Skinny on Net Impact Carbs

If you’ve ever bought a meal replacement bar, you’re probably familiar with the the term net impact carbs. Simply stated, net impact carbs refers to the amount of carbs in a product that promote an insulin response. As you may know, carbs can raise blood sugar levels, causing insulin levels to spike.

Why is this important? Well, high blood sugars levels cause the pancreas to secrete insulin in large amounts. Insulin is a storage hormone. While its primary purpose is to neutralize blood sugar, it also is responsible for converting sugars into body fat as well as inhibiting the conversion of stored fat into energy. When carbohydrates are ingested, the pancreas secretes insulin to clear blood sugar from the circulatory system. Depending on the quantities and types of carbs consumed, insulin levels can fluctuate wildly, heightening the possibility of fat storage.

To mitigate insulin response, many nutriceuticals substitute high-glycemic carbs with alternative carb-based nutrients called sugar alcohols (also called polyols), which have a negligible impact on blood sugar. Theoretically, by limiting carbohydrates that increase insulin levels (i.e. net impact carbs), you can minimize the deleterious effects of insulin and promote better weight management.

But while it’s true that carbohydrates that raise blood sugar can be detrimental to maintaining low body levels, the concept of net-impact carbs isn’t as clear cut as it may seem. Generally speaking, meal replacement bars also contain a combination of protein, fat and/or fiber. This slows digestion and moderates glycemic response, thereby reducing the fat-storing effects of insulin.

On the plus side, the sugar alcohols (such as maltitol, mannitol, sorbitol, Xylitol, and HSH) used as replacement carbs are not able to be fully absorbed by the body and thus are lower in calories than “standard” carbohydrates. They contain between two to three calories per gram as opposed to the four calories per gram in glucose, fructose and galactose (glycerol, a sugar alcohol found in many bars due to their propensity to keep foods moist and improve shelf life, also contains four calories per gram). Since calories do count and ultimately have the greatest effect on whether you gain or lose body fat, this is a benefit for those seeking to lose weight.

Bottom line: Nutrition is a complex subject and it’s important to understand that many factors come into play when designing a regimented eating plan. From an insulin standpoint, the overall effect of net impact carbs on body composition will be negligible. Significantly more important is the nutritional content and caloric density of the food source.

Stay Fit!

Brad