Not all carbs are created equal. Especially when it comes to their impact on our blood sugar. The glycemic index measures how a carbohydrate-containing food impacts our blood glucose. Carbs, therefore, can be viewed in two buckets: impact & non-impact. A high-impact or high glycemic index food will raise blood glucose more than a food with a medium or low glycemic index -- non-impact.
Meats and fats don’t have a GI because they do not contain carbohydrate.
Refer to this chart from Diabetes.org for an extensive listing of foods and their GI.
Low GI Foods (55 or less)
- 100% stone-ground whole wheat or pumpernickel bread
- Oatmeal (rolled or steel-cut), oat bran, muesli
- Pasta, converted rice, barley, bulgar
- Sweet potato, corn, yam, lima/butter beans, peas, legumes and lentils
- Most fruits, non-starchy vegetables and carrots
Medium GI (56-69)
- Whole wheat, rye and pita bread
- Quick Oats
- Brown, wild or basmati rice, couscous
High GI (70 or more)
- White bread or bagel
- Corn flakes, puffed rice, bran flakes, instant oatmeal
- Short grain white rice, rice pasta, macaroni and cheese from mix
- Russet potato, pumpkin
- Pretzels, rice cakes, popcorn, saltine crackers
- melons and pineapple
Impact carbohydrates are ones that have a big impact on our blood sugar level or a high glycemic index. These carbs digest rapidly into the bloodstream -- think candy and other packaged sweets. Because they’re in the bloodstream so quickly they’re immediately used by the body -- sugar rush! Unless you’re going to burn that energy off through physical movement of some kind, the carbs will simply get stored as body fat. Two interesting scenarios to note: you’ll frequently see candy and similar items at the tables of pit stops during running races, the idea here being that they’re a comfort, act fast and you’ll likely burn all the carbs. Conversely, if you eat candy at your desk job all day and have limited physical activity, it’s going to add weight and add it fast at that.
High GI carbohydrates in and of themselves in the typical American diet usually leads to weight gain and a smattering of potential health problems. However, if used during strenuous exercises, races, etc.., that can be a great way to boost energy without getting the unwanted stored body fat. Don’t make excuses for eating them though! Be honest with yourself about why you’re eating them :) For a sedentary lifestyle, or taking them for daily energy needs, avoid “bad” high glycemic foods. If you’re going that route, you can opt for potatoes and short grain rice as examples.
If your daily carbohydrate intake is loaded with high GI carbs you’ll likely put on weight. They kill your energy levels and can make you feel tired and even mess with your head i.e. giving you the blues. If you deal with a mood disorder, watching your carb choices -- and ALL foods -- can have significant effects -- good or bad.
There are some athletes that swear by high GI carbs as a tool for post-workout recovery due to their ability to get nutrients into the bloodstream quickly. Not something that’s been well-researched, but an interesting perspective/potential. If I can start eating sour patches after my work-outs because it’s healthy, the world will be a better place :)
The low glycemic index or non-impact or low-impact carbohydrates on the other hand digest at a much slower rate in the bloodstream. The release of glucose in the body prolongs the release of energy, also making insulin spikes unlikely. With a slower rate, comes more sustained energy levels.
For everyday living, low GI carbohydrates are the way to go. They’ll help you to sustain energy levels throughout the day, which translate to better mental clarity, alertness, emotional improvement and fuel in the tank to get physical.
Now that you know the difference between the two carb types, you can use both of them to serve their very unique purposes instead of completely casting them out.
the Glycemic Index & Diabetes
Carbohydrates with a high glycemic index have been frequently linked to type 1 & type II diabetes. These carbohydrates tend to be mass-produced, widely available and convenient for our own the go lives. Branding and packaging along with an unprecedented amount of customer touchpoints have made it virtually impossible to resist. You’ll find “healthy protein bars” at a deli, airport, school cafeteria and supermarket. They’re everywhere. A full rundown on diabetes is beyond the scope of this post, but focusing on whole foods and a shift of focus to foods with low glycemic indexes are definitely going to improve your health across the spectrum.
Net Carbs -- how to calculate
Net carbs are derived by taking the total carb count and then subtracting the grams of fiber. So for instance, if a food has 10 grams of carbohydrates and 7 grams of fiber, then the net carb is 3 grams. Fiber is imperative to gut health and the digestive system and interestingly does not contain any calories because the body doesn’t absorb it. Net carbs, therefore, are an important metric in the keto diet because they give us our true carbohydrate count.
The are many daily recommendations of fiber so as always it’s important to be cognizant of your body and how it reacts to foods, but as general rule women should aim for 25 per day and men 38g per day.
As I’m sure you guessed by now, high glycemic carbs are generally very low in fiber. Therefore high glycemic carbs tend to have a high impact on your net carb count which in turn is going to affect how you eat on your keto diet -- better / low glycemic carbs equal more carbs!
We’ll close by saying that you don’t need to eliminate high-glycemic carbs from your diet, but if you’re following a keto or low-carb diet, be conscious of the what, why and when. And when you do opt for high-glycemic foods balance them out with low-glycemic foods to get the most out of your diet & performance.