When talking about fitness and nutrition, there are topics such as the Glycemic Index and high-glycemic carbohydrates vs. low-glycemic carbohydrates that come up in conversation. Especially when people talk about weight loss and nutrient timing. But what exactly does this mean for your specific health goals? What is the Glycemic Index? What is the difference between high- and low-glycemic carbs? How do we strategically these carbs & how does it impact your body, your workouts, and your overall health? Let take a look.
Glycemic Index
The Glycemic Index is a system that measures the impact of carbohydrates on your blood sugar. This index rates food on a scale of 0–100, with foods that cause the greatest impact on blood sugar (i.e.: High-GI foods) ranked somewhere between 70–100, while foods that cause the least impact on blood sugar (ie: Low-GI foods) are assigned a number somewhere between 0–55. So basically, high numbers equal high-glycemic carbs and low numbers equal low-glycemic carbs. Genius!
So why does this matter and why should you care about these numbers when choosing your daily foods and planning your weekly meals?
Well, for one thing, the human body functions and performs at its best when blood sugar is kept stable. If your blood sugar dips too low, for instance, you may feel light-headed or lethargic and experience intense sugar cravings or hunger. If your blood sugar spikes too high, on the other hand, your body releases insulin in an attempt to stabilize your blood sugar, and it does this by converting the excess sugar in the blood into stored fat. Not what you want when trying to hit your body goals!
Plus, this release of insulin as the body attempts to normalize itself can have a reverse effect, causing your blood sugar to dip too low. This causes a rollercoaster effect in your body, leading to extreme energy spikes and crashes, as well as the corresponding sugar cravings (and possible junk food binges) as your body fights to regain balance.
Because of this, it may seem as though low-glycemic carbs are the Holy Grail of healthy eating and high-glycemic carbs should be avoided like the plague; however, this isn’t quite accurate. There are times when consuming foods that rank high on the GI scale are desirable. The type of carbohydrates you eat impacts your blood sugar, which in turn affects your energy, weight, fat storage, and physical performance. The Glycemic Index helps you understand and separate high-glycemic foods from low in order to target, improve, and achieve individual body goals.
Difference Between High- and Low-GI Foods
So what’s the difference between high- and low-glycemic carbs? High-glycemic carbohydrates are foods that cause a significant spike in blood sugar. They are converted to simple sugars (aka: glucose) by the digestive system very quickly, causing a large and rapid spike in blood sugar, which can negatively impact insulin, energy levels, and fat storage, as discussed above.
Although this might initially seem like a negative, when it comes to high-glycemic carbohydrates, it’s important to remember that just because a food is ranked high on the Glycemic Index doesn’t automatically mean it’s ‘bad’. Like any food you choose to incorporate into your diet, the quality and nutrient value of the foods you consume determine its worth and place in your daily diet. With that in mind, there are many healthy, whole food sources of carbohydrates that have a high-glycemic index rating, yet are an essential part of a balanced diet, providing the body with phytonutrients, vitamins, and minerals.
Healthy High-Glycemic Carbohydrates
Cooked potatoes
Cooked carrots
Fruit juice, fresh-pressed
Bananas
Mango
Pineapple
Watermelon
What you DO want to stay away from on the high-glycemic carb scale, however, are highly processed and refined foods such as:
White bread
Chips and crackers
Instant oatmeal (which not only is stripped of nutrient value, but typically has TONS of added sugar too)
“White” carbs from flour, pasta, and rice
Reducing or eliminating your intake of these highly processed, high-glycemic carbohydrates while focusing on healthier high-glycemic carbohydrates from whole food sources is an excellent approach to keeping your nutrition and fitness goals on track, while also reducing your risk of insulin resistance and its corresponding chronic diseases, such as diabetes, liver, and heart disease.
In contrast to high GI carbohydrates, low-glycemic carbohydrates cause very little impact or increase in blood sugar when eaten in normal portion sizes. Since these carbs are the ones that keep your blood sugar (thus insulin, energy, and fat storage) balanced and healthy, these are the carbohydrates that should make up the majority of your daily carbohydrate intake.
Healthy Low-Glycemic Carbohydrates
Quinoa
Steel-cut oats
Whole grains such as millet, amaranth, farro, and wild rice
Beans and legumes
Non-starchy vegetables
Most fresh fruit
Sweet potatoes
From the food list above, a key factor in low-glycemic carbohydrates is fiber. Fiber is a type of carbohydrate that your body can’t digest, which directly impacts the digestion and absorption of sugars found in those foods. In other words, low-glycemic carbohydrates (aka: complex carbs) have a high fiber content, which slows the absorption of sugar in the body, helping to minimize any blood sugar spikes and moderate the release of insulin.
Energy from low-glycemic carbohydrates also serves another body-healthy purpose: Any excess fuel found via low-GI carbs is funneled to the liver and muscles, where it’s stored as glycogen, a backup source of energy which the body breaks down and converts to glucose on an as-needed basis instead of storing it as body fat like high-glycemic carbs do. This is a key factor in weight loss and weight maintenance; helping your body use or store excess fuel in a very proactive way that supports lean muscle instead of fat tissue.
When to Eat What
Now that you know the difference between high- and low-glycemic carbohydrates, when is the optimal time to consume each?
Optimal High-Glycemic Carbohydrate Consumption
Although keeping blood sugar stable by consuming mainly low-GI foods is a good aim and a wise guideline, there are exceptions. Consuming high-glycemic carbohydrates anywhere between 15 minutes to 2 hours post-intense training helps your body start to replenish and recover. Since both glucose (immediate energy/sugar) and glycogen (stored energy) were used during physical activity, the body’s energy stores have been depleted, leading to a catabolic state where the body pulls fuel from the liver, fat, and muscles. Consuming high-glycemic carbs immediately after those training sessions moves the body from a catabolic state to an anabolic state by boosting blood sugar and spiking the body’s release of insulin. This moves much-needed nutrients and glucose back to your muscles, which is critical for muscle and tissue repair, recovery, and growth.
This is not an excuse to consume anything you want, though! As you’ve heard many times before: You can’t out-exercise a bad diet! So as much as you may like to justify it, following your high-intensity workout with a bag of Doritos and a couple slices of white bread really isn’t the optimal way to target and accomplish your body goals. Instead, this 2-hour post-exercise window is a great time to replenish your body with some of those healthy high-glycemic carbohydrates mentioned above. For example, having a post-workout, high-glycemic meal such as a whole wheat burrito with brown rice, veggies, and lean protein, or a ezekial bread with lean protein, fresh vegetables, and avocado washed down with some fresh-pressed juice would be an ideal way to take advantage of this window. A key component here is also pairing these high-GI carbs with protein, which your body also needs post-workout for optimal recovery, repair, and growth.
Optimal Low-Glycemic Carbohydrate Consumption
Because low-glycemic foods are high in fiber and assimilate at a slower rate, consuming normal-sized portions of low-glycemic carbohydrates throughout the majority of your day is best for sustained energy balance, hunger maintenance, and weight loss.
It’s also important to note that pairing low-glycemic carbs, such as raw vegetables, with high-glycemic carbs, such as pasta or bread, actually lowers the total glycemic impact on your blood sugar. The fiber from the low-GI carbs slows the digestion and absorption of the sugars from the high-GI carbs, which is yet another reason to sneak as many raw veggies (or other low-GI foods) into your daily diet as possible.
When using the Glycemic Index to determine your ideal carbohydrate consumption, don’t forget that a number of other factors come into play when it comes to a balanced diet. Factors such as cooking time, ripeness, food processing, and serving size, as well as food pairing (i.e.: what other foods, such as proteins and fats, are paired with your carbohydrates) all impact blood sugar, digestion, and absorption, directly impacting your overall health, physical performance, weight loss, and risk for chronic disease. Taking this into account when crafting a well-balanced diet that incorporates both healthy high- and low-glycemic carbohydrates is key to understanding how to utilize nutrition in order to hit your target health goals.