Understanding Glycemic Index and Its Impact on Energy Levels

[01dragonslayer]

The glycemic index (GI) tells you how quickly foods raise your blood sugar. High-GI foods make your blood sugar rise quickly and then drop quickly, while low-GI foods release glucose slowly, giving you energy for a longer time. When you choose whole grains, legumes, and fruits instead of refined carbohydrates, you'll feel more awake and happy. Combining high-GI foods with protein or healthy fats can help keep blood sugar levels stable. Getting this balance right will make sure you have steady energy all day long.

The Science Behind Glycemic Index and Blood Glucose Regulation​

When you eat carbs, your body breaks them down into glucose, which gets into your blood and causes an insulin response. The glycemic index (GI) of the food affects how quickly this process happens.



Foods with high GI, like white bread and sugary drinks, cause your blood sugar to rise quickly. It makes your pancreas release a lot of insulin to deal with the sudden rise. It often makes you feel tired later. On the other hand, low GI carbs like beans, whole grains, and most vegetables release glucose slowly, which keeps blood sugar levels more stable.

How High-GI Foods Create Energy Peaks and Crashes​

High-GI foods like white rice, sugary cereals, and processed snacks create a predictable pattern in your body's energy systems. When consumed, they rapidly convert to glucose, causing sharp blood sugar spikes that initially boost your energy levels.

To handle this flood of glucose, your pancreas releases a lot of insulin. This big insulin response often takes too much sugar out of your blood, which makes you feel tired and crave more carbs.

Lower glycemic foods release glucose slowly, so you stay full longer. This steady method prevents your blood sugar from riding a roller coaster and keeps you moving without any highs or lows.

Benefits of Low-GI Foods for Sustained Energy Throughout the Day​

Low-GI foods serve as the foundation for sustainable energy management throughout your day. Your body digests these nutrient-dense foods more slowly, which means that glucose is released slowly over time. It stops the big energy swings that happen with high-GI foods.

Eating low-GI foods all the time keeps your metabolism steady, which has many benefits. For example, your mental and physical performance stays steady, and you don't have the mid-afternoon crashes that make you less productive. These foods also help you control your appetite better because they keep you full longer.

A low-GI diet helps individuals with diabetes manage their condition more effectively by promoting steady blood sugar control and potentially lowering medication requirements. This way of eating helps keep your metabolism healthy in the long term by lowering insulin needs and inflammation, which are two important things that help stop chronic diseases from developing.

Practical Guide to Replacing High-GI Foods in Your Diet​

When you know how to replace high-GI foods with healthier ones, you don't have to make big changes to your diet. By swapping white bread for whole grain, you allow carbohydrates to be absorbed gradually, which helps maintain balanced energy levels.

Opting for steel-cut oats or Greek yogurt with fruit in the morning can help maintain steadier blood sugar levels compared to sugary cereals. If you want rice, go for basmati or brown rice instead of short-grain white rice.

To make your meals more balanced, use sweet potatoes or legumes instead of starchy potatoes. Even small changes, like switching from fruit juice to whole fruits, can have a big effect on how much energy you have. These planned swaps help you keep your blood sugar stable while still eating meals that fill you up.

Balancing GI Levels for Optimal Physical and Mental Performance​

You need to learn how to keep your glycemic index levels in check all day long if you want to be at your best physically and mentally. Eating different GI foods at the right times can give you more energy when you need it most. High GI foods before hard workouts give you quick energy, and low GI foods help you stay focused during long work sessions.



To keep your mind clear, don't eat any higher GI foods with protein or healthy fats. For your brain to work at its best, it needs a steady supply of glucose. It is why low- to medium-GI foods are best for workdays. Overnight oats with nuts are great for morning meetings, and yogurt and berries instead of processed snacks can help keep you from getting tired in the afternoon.

Always match your GI intake to your activity level for consistent energy without the peaks and valleys.

Frequently Asked Questions​

Do preparation techniques alter the glycemic response of foods?​

Yes, cooking methods directly impact GI values. When you boil, steam, or briefly cook foods, you'll maintain a lower GI. Overcooking, frying, or processing breaks down starches, raising GI considerably.

Can Stress or Sleep Affect How My Body Responds to GI?​

Yes, both stress and sleep impact your glycemic response. When you're stressed or sleep-deprived, your body's insulin sensitivity decreases, potentially causing higher blood sugar spikes even from low GI foods you'd normally tolerate well.

Are Artificial Sweeteners Better Alternatives to High-Glucose Sugars?​

While artificial sweeteners don't raise blood sugar like high-GI sugars, they're not ideal alternatives. You'll avoid glucose spikes, but they may affect gut health and potentially increase cravings for sweet foods long-term.

How Quickly Do Low-Gi Foods Improve Energy After Making Dietary Changes?​

You'll notice improved energy stability within days of switching to low-GI foods. While some benefits appear quickly, you'll experience the full impact on your sustained energy levels after 2-3 weeks of consistent changes.

Should Children's Diets Be Planned Around Glycemic Index Considerations?​

Yes, you should consider GI when planning children's diets. It helps prevent energy crashes, improves concentration, and establishes healthy eating habits. Focus on balanced meals with low-GI options rather than strict GI restrictions.

 

[01dragonslayer]

 

[01dragonslayer]

The glycemic index (GI) charts below illustrate how different carbohydrates affect your blood sugar.2 This can help you fine-tune your meals to keep your blood sugar within a normal range.

Illustration by Joules Garcia for Verywell Health

Low, Medium, and High Glycemic Index Charts​

Glycemic index (GI) values can be broken down into three ranges. Foods with a low GI won't raise your blood sugar as much as foods with a medium or high GI.2

• Low GI: 55 or less
• Medium GI: 56 to 69
• High GI: 70 to 100

The following charts highlight low, medium, and high GI foods:3

Low-GI Foods (55 or Less)
Foods	GI
Apple	36
Apple juice	41
Apricots	50
Banana	51
Barley	28
Beans (kidney)	23
Beans (pinto)	39
Beans (black)	31
Blueberries	40
Carrots, boiled	39
Carrots, raw	16
Chapatti	52
Cherries	29
Chickpeas	28
Chocolate	40
Dates	42
Eggs	0
Grapefruit	26
Ice cream	51
Kidney beans	24
Lentils	32
Mango	51
Orange	43
Orange juice	50
Peaches, canned	43
Pears	33
Plantain	55
Raspberries	30
Rice noodles	53
Rolled oats	55
Skim milk	37
Soya beans	16
Soy milk	34
Pasta (whole grain), spaghetti4	54
Specialty grain bread	53
Strawberries	40
Strawberry jam	49
Sweet corn	52
Taro, boiled	53
Udon noodles	55
Vegetable soup	48
Whole milk	39
Yogurt, fruit	41

Medium-GI Foods (56 to 69)
Foods	GI
Angel food cake	67
Basmati rice	54
Brown rice	68
Clover honey	59
Couscous	65
French fries	63
Millet porridge	67
Muesli	57
Oat bran cereal	61
Orange juice, unsweetened	53
Pasta (white), spaghetti4	58
Pineapple	59
Popcorn	65
Pound cake, unfrosted	55
Potato chips	56
Pumpkin, boiled	64
Raisins	66
Soda, non-diet	59
Sweet corn, canned	60
Sweet potato, boiled	63
Wheat flake biscuits cereal	69
Wheat roti	62

High-GI Foods (70 to 100)
Foods	GI
Candy (jelly beans)	80
Cookies (chocolate chip)	70
Cornflakes	81
Instant oatmeal	79
Potato, boiled	78
Potatoes, instant mashed	87
Rice milk	86
Rice porridge	78
Rice crackers	87
Short-grain rice	76
Unleavened wheat bread	70
Watermelon	76
White rice, boiled	73
White bread (wheat)	75
Whole wheat bread	74

Glycemic Index Explained​

GI ranks carbohydrates on a scale of 1 to 100 based on how much they raise blood sugar. When you have type 2 diabetes, one of the best ways to control your glucose levels is to eat foods that don't cause major blood sugar (glucose) spikes. Foods with a higher GI value are more likely to spike your blood sugar than foods with a lower GI.


Processed foods such as candy, breads, cake, and cookies have a high GI, while whole foods such as unrefined grains, non-starchy vegetables, and fruits tend to have a lower GI.


Carbohydrates with a low GI value are digested, absorbed, and metabolized more slowly than their high-GI counterparts. They typically cause a lower and slower rise in blood glucose and, subsequently, insulin levels as well.2


Foods that are primarily fat or protein are not included in the index because they have a minimal impact on blood sugar levels.

Variables That Can Affect Glycemic Index​

The glycemic index of any particular food can vary depending on factors like the way it's cooked. Boiled vegetables, for example, may have a different GI than the same vegetable that has been sautéed. A very ripe fruit will also have a higher GI than an underripe fruit.

How Glycemic Index Is Measured​

Glycemic index values were developed by a rigorous testing process using 10 or more people for each food.5


Researchers measured blood sugar levels of healthy volunteers before and two hours after eating 50 grams of the same digestible carbohydrate (the test food). The points were then plotted on a graph, and researchers determined the area under the curve (AUC) of their glucose response.


At a separate date, the same 10 people consumed 50 grams of pure glucose (the reference food), and researchers again measured each person's glucose response AUC two hours after consumption.


The GI value of the test food is then calculated by dividing the glucose AUC for the test food by that of the reference food for each person. The final GI value is an average of those 10 numbers.


Ultimately, the GI value is the average person's blood sugar response to a specific carbohydrate. Individual responses may vary based on other factors, including other foods eaten in combination with the carbohydrate.

Benefits of the GI System​

Since it's the carbohydrates in food that raise blood sugar, understanding GI can help you figure out which foods are best for glucose management.6


Among the benefits of following the GI list when planning your meals:

• It helps you be more mindful of your carb choices without fully restricting or severely limiting your intake.
• If you aim for a low-GI diet, you'll naturally be focusing on whole grains, fruits, vegetables, and legumes, as opposed to the higher-GI end of the spectrum, which includes more processed foods.
• Depending on your health goals, following a GI-based diet might mean you'll be able to rely less on standard dieting measures, such as calorie counting or regimented portion control.
• Simply being more mindful of your carb choices rather than severely limiting them can also be more sustainable in the long run, as compared to more restrictive diets.

Charday Penn / Getty Images

Shortcomings​

Critics of the GI system note it has several flaws that can make it an unreliable measurement. GI looks strictly at the carb count. Basing a diet around GI only means you would be ignoring a lot of other helpful information to determine the true health value of a food.


The GI index doesn't take into account:

• How much food is being eaten
• Other nutrients such as protein, fat, vitamins, minerals, and antioxidants
• Other components of the meal, which can change the effect of blood sugar rise

For example, eating an apple on its own may result in a different blood glucose response than if you ate it with some peanut butter. Protein and fat can delay carbohydrate metabolism and, therefore, result in a slower blood sugar rise.

Why are foods like meat and butter not on the glycemic index?​

The glycemic index (GI) is a measure of how much the carbohydrates in a food affect blood sugar. Since foods like meat and butter don't contain carbohydrates, they are not included.

Glycemic Index vs. Glycemic Load​

To counteract some of the issues with glycemic index, researchers developed the glycemic load (GL) measurement. Unlike GI, GL accounts for the quantity of the food being eaten.7

• Glycemic index is based on eating 50 grams of a specific food
• Glycemic load is based on eating a standard serving size of a specific food

Glycemic load is calculated by multiplying the GI value by the number of carbohydrates (in grams) per serving, then dividing that number by 100.


For example, an apple has a GI of 40 and contains 15 grams of carbs. (40 x 15)/100 = 6, so the glycemic load of an apple is 6.

Glycemic Load Values​

In theory, foods with a low GI would also have a low GL, but that isn't always the case. Research from the International Carbohydrate Quality Consortium (ICQC) suggests that glycemic load is a more reliable indicator of how a particular carbohydrate affects blood sugar.8


Like GI values, GL values can also be broken down into three ranges:2

• Low GL: 10 or less
• Medium GL: 11 to 19
• High GL: 20 or more

Some foods fall under the same category for both glycemic index and glycemic load. For example, apples and oranges are both low GI and low GL, while cornflakes and boiled potatoes have both high GI and high GL.


But for other foods, the glycemic index and glycemic load are different. For example, bananas have a low GI but a medium GL, and dates have a low GI and a high GL.


A food that perhaps best highlights the difference between glycemic index and glycemic load is spaghetti. Both whole grain spaghetti and spaghetti made from white flour are considered low GI (48 and 49, respectively). However, whole wheat spaghetti has a medium GL (14) while regular, white flour spaghetti has a high GL (20).

Calculating Your Daily Glycemic Load​

Try to keep your daily glycemic load under 100. To calculate your daily glycemic load, add up the GL of each food you consume throughout the day.

Glycemic Load Chart for Common Foods​

The following charts highlight low, medium, and high GL foods based on data from the Linus Pauling Institute at Oregon State University.9

Low-GL Foods (10 or less)
Foods	GL
Apple	6
Carrots, boiled	1
Cashews	2
Kidney beans	8
Lentils, dried and boiled	7
Orange	5
Peanuts	1
Pear	4
Skim milk	4
Watermelon	8
White bread (wheat)	10

Medium-GL Foods (11 to 19)
Foods	GL
Banana	13
Pearled barley, boiled	11
Puffed rice cake	17
Spaghetti, whole wheat	14

High-GL Foods (20 or more)
Foods	GL
Brown rice	20
Cornflakes	20
Dates	25
Potato, boiled	25
Spaghetti	20
White rice	35

The Best Way to Test a Food's Impact​

The American Diabetes Association states that carbohydrate amount (grams of carbohydrates) and available insulin may be the most important factors influencing blood sugar response after eating and should be considered when developing an eating plan.10


The most reliable way to assess how your body is affected by certain foods is to test your blood sugar two hours after a meal or use a continuous glucose monitoring system.


For most people, an ideal blood sugar result is less than 180mg/dL two hours after the start of a meal.11 If you are not sure of what your target blood sugar should be, discuss it with your physician.