how to tell which carbs to eat and which to avoid
Most carbs are the same in calories the only difference being at what rate does your body burn the calories in that carb. Good carbs contain fiber which slows absorption of the sugar content and other nutrients. This is the case with leafy greens and other fibrous fruits and vegetables. Based on these good carb characteristics they fall into the group of foods which rate low on the “low glycemic index.”
To set the glycemic index of a particular food, say a pasta, ten volunteers eat 50 grams (about 2 ounces) of pasta in the morning after fasting, and their blood sugar is measured over the next two hours. The total rise in glucose during this two-hour time period is calculated. Several days later, the same 10 volunteers drink 50 grams of glucose, and have their blood sugar measured in the same way over the next two hours. Then the two glucose sums are compared, and the difference in value between the test food and the ingested glucose becomes the glycemic index value for the tested food. You can find the glycemic index value of hundreds of foods in a database maintained by the University of Sydney, Australia, at www.glycemicindex.com.
As simple as it sounds, the Glycemic Index can be a challenge to utilize in real life. Foods don't always affect your blood sugar the way you would expect them to based on their glycemic index, due to a number of variables such as times between meals, physical activity, water consumption and more.
That take home is, it's also important to know that unprocessed foods such as lean proteins coupled with fresh fruits, vegetables and greens will always be better for you low carb frankenfoods made in a laboratory which are generally high in fat and chemicals.