When diagnosed with diabetes or any other metabolic condition, many people start searching around for the right diet to help manage their blood sugar.

Of course, a healthy diet is a cornerstone of well-being, but it can become a bit more complicated for those with blood sugar control issues. Is fruit okay? What about starchy vegetables?

One of the most well-known diet tools for people with diabetes or prediabetes is the glycemic index. Since the early 1980s, people have relied on this index to guide them in making healthy choices for blood sugar regulation.

But what is the glycemic index, and is it really the best choice for diabetes?

This article will explore how foods are rated on the glycemic index, the benefits of following a low-GI diet, and why low GI may not be enough if you really want to tackle diabetes head-on.

What Is The Glycemic Index?

The glycemic index (GI) is a tool that was developed by Dr. David J. Jenkins back in 1981. The primary purpose of the GI is to help people understand how specific foods impact their blood sugar. Just like calorie counting, or any other system that tracks the components of foods (such as macros), the glycemic index is meant to guide people that are sensitive to carbohydrates (such as those with diabetes).[1] 

While the glycemic index is a tool and not a diet in itself, many people follow a "low-glycemic index diet," which simply refers to a diet that includes foods that rank low on the index. Many people find this type of diet easy to follow because rather than tracking calories or carbohydrates, they just fill their plates with low GI foods and don't have to give it much thought. 

The GI foods lists were originally developed to help people with diabetes, but many people also leverage low-GI eating to help with weight loss. 

What Makes A Food Low GI?

The glycemic index rates foods on a scale of 1 to 100 and is divided into three general categories:

  • Low GI: 1 to 55
  • Medium GI: 56 to 69
  • High GI: 70 and higher

A few examples of high glycemic index foods include white rice, watermelon, and sugary breakfast cereals. On the other hand, low glycemic index foods include sweet potatoes, brown rice, lentils, and kidney beans. Notice that these foods are not necessarily low-carb.

To assess the GI of a food, its impact on blood sugar levels is measured against 50 grams of pure glucose (which has a GI of 100). Since sugar (glucose) will raise blood sugar most efficiently, this serves as a marker against which other foods can be tested. 

Put simply, the lower the GI of a food, the less it will impact your blood glucose levels.

Factors that Affect A Foods GI

If a food doesn't contain any carbohydrates, then it doesn't have a glycemic index; therefore, you won't find items like meat, eggs, and chicken on the GI foods lists. This doesn't mean that these foods should be avoided on a low GI diet, but rather there is no concern around blood sugar, so you don't need to track them.

So then the question becomes; what makes carbohydrate foods rank higher or lower on the GI? Several factors come into play when determining the impact that food has on blood sugar. For example: 

Fiber And Net Carb Content

Fiber plays a big role in the glycemic impact because of all the different types of carbohydrates out there; dietary fiber is the only one that is not digested. Therefore, any amount of fiber that contributes to the total carb content can effectively be discounted from the total. 

Let's say, for example; you have two pieces of bread; both contain 10 grams of total carbohydrate, but one has 5 grams of fiber, while the other contains 1 gram of fiber. The net carbohydrates would then look like this:

10 grams of carbs - 5 grams of fiber = 5 net carbs

10 grams of carbs - 1 gram of fiber - 9 net carbs

The second piece of bread would greatly impact your glycemic index because it simply has more digestible carbs.[2]

An example would be a fiber-rich bread made primarily with whole grains that were not highly refined versus a piece of white bread. 

Types of Sugar 

When you zoom in on a complex carbohydrate, you'll find chains of glucose (single sugar molecules) strung together in various formations. Depending on the specific formation of the carbohydrate molecule, it will either break down quickly or slowly. The faster the carb is broken down, the quicker it can get into your bloodstream and create a rise in your blood sugar.

Amylose, which is a straight chain of glucose molecules, takes longer to break down than amylopectin, which has many branches. Carbohydrate sources will have varying amounts of each type of complex carb, also known as starch. If a food is rich in amylose, it's more likely to rank lower on the GI scale, while high amylopectin foods will rank higher.[3,4]

Macronutrient Composition 

Most foods are not made up of 100% carbohydrates and contain at least some amount of fat and protein. Both fat and protein are slower to digest than carbs and, therefore, will result in a net lower GI impact due to the food matrix.[5]

For example, while both avocado and apples are both fruit, avocado ranks much lower on the GI due to its significant fat content. Specifically, an apple comes in with a GI of 36, while avocado ranks at 15. 

Cooking Method and Ripeness

The cooking method you use can break down fiber and starch, resulting in a higher GI due to enhanced bioavailability of the glucose molecules in the food.

The same goes for ripe versus unripe fruit. While fruit is still ripening, it contains higher levels of complex carbohydrates, which eventually break down into more simple carbs as the fruit ages and matures. This is why ripe fruit is sweeter than unripe.[6]

Is the Low Glycemic Diet a Good Choice For Diabetes?

While the low GI diet was created to help people with diabetes, there is some debate as to whether this is actually an ideal diet plan for people with blood sugar issues, so let's explore the pros and cons a bit.

Pros Of The Low-Glycemic Diet For Diabetes

One of the pros of low-GI eating is that it focuses on foods that won't spike your blood sugar. By avoiding high-GI foods, you're taking an essential step in regulating blood sugar and not worsening symptoms of diabetes. 

Research shows that compared with higher GI diets, a low GI diet can improve blood glucose homeostasis and HbA1c levels in people with diabetes – which is certainly a good thing.[7]

Moving away from a high GI diet also tends to be an all-around good idea as many foods with a high GI value are also heavily processed.

Another pro of low-GI diets is that they're generally easy to follow. Once you have a good idea of the rules of the game (which foods are high vs. low on the GI scale), it can be pretty straightforward to choose low-GI foods without giving it too much thought. 

However, with all that being said, there are some significant downsides to the low-GI diet to consider.

Cons Of The Low-Glycemic Diet 

While low-glycemic does indicate that the foods on your plate won't spike blood sugar, it doesn't fall into the low-carb category. 

Why should this matter? Research shows that low-carb diets not only help you to control your blood sugar while you're eating, but they also help to re-sensitize your cells to insulin. This means that following a low-carb diet could help you turn your diabetes and insulin resistance around. 

Following a low-GI diet doesn't produce the same results due to the number of carbs that are still included in the diet. It takes a certain amount of carb restriction to allow for insulin resensitization, and unless you consciously make low-carb, low-GI choices, there is no guarantee you'll get there on the low-GI meal plan.[8]

Another significant downfall of the low-GI diet is that the lists you follow with GI rankings don't necessarily consider the amount of food you eat. 

For example, if you consume one apple, it has a GI of 36, but what happens to your blood sugar if you chop up a bunch of apple slices and end up eating two apples worth? This could result in a blood sugar spike due to the sheer amount of glucose in your meal. 

There is a term called the "glycemic load (GL)," which takes into account the GI of each individual food item in your meal, and often the GL ends up ranking much higher than you would expect.[9] 

And finally, just because a food ranks low on the glycemic index doesn't necessarily mean it's healthy. These days there are more low-GI packaged foods than ever before. Manufacturers add all kinds of fillers, fake sugars, and artificial ingredients to transform foods that would typically rank high-GI into low-GI alternatives. If you're solely relying on a low-GI diet to try to attain your health goals, it misses a big piece of the puzzle – nutrient density.

And whether you're trying to manage diabetes, lose weight, or just clean up your diet, your body needs foods that are rich in a variety of nutrients if you want to feel your best. 

The Verdict: Does Low GI Work For Diabetes?

Could someone successfully follow a low-GI diet for diabetes management? Certainly. When you reduce foods in your diet that spike your blood glucose, it helps to manage sugar spikes which is a very good thing for diabetes.

With that being said, following a low-GI will likely not do much to help you re-sensitize your cells to insulin and turn your condition around. It also doesn't account for food quality and quantity, which can end up creating more harm than good. 

Therefore, while this diet can work, it is not necessarily the best option.

On the other hand, when you focus on consuming a diet that's rich in real, whole foods that are also low carb, you give your cells a chance to desensitize themselves to insulin and provide your pancreas with a much-needed break from trying to pump out insulin to manage your carb intake. 

The Takeaway

While consuming a low GI diet can certainly help with glucose control, it doesn't account for the number of carbohydrates you consume. Therefore, you may miss out on the benefits you can get from low-carb dieting.

If you're managing type 2 diabetes, glycemic control is vital. But with the addition of reduced carbohydrates, you can re-sensitize your cells to insulin, which may actually help you turn the entire condition around.

Low GI dieting also doesn't address the importance of healthy eating, which plays a significant role in the outcome of any metabolic condition.

To learn more about your dietary options for successfully managing diabetes, check out the BioCoach App, where you'll receive tips, guidance, and education on all things diabetes.

On the other hand, when you focus on consuming a diet that’s rich in real, whole foods that are also low carb, you give your cells a chance to desensitize themselves to insulin and provide your pancreas with a much-needed break from trying to pump out insulin to manage your carb intake. 


  1. https://www.nhs.uk/common-health-questions/food-and-diet/what-is-the-glycaemic-index-gi/
  2. Jenkins, David JA, and Alexandra L. Jenkins. "Dietary fiber and the glycemic response." Proceedings of the Society for Experimental Biology and Medicine 180.3 (1985): 422-431.
  3. Kabir, Morvarid, et al. "Dietary amylose-amylopectin starch content affects glucose and lipid metabolism in adipocytes of normal and diabetic rats." The Journal of nutrition 128.1 (1998): 35-42.
  4. Eleazu, Chinedum Ogbonnaya. "The concept of low glycemic index and glycemic load foods as panacea for type 2 diabetes mellitus; prospects, challenges and solutions." African health sciences 16.2 (2016): 468-479.
  5. Wolever, Thomas MS. "Effect of macronutrients on the glycemic index." The American Journal of Clinical Nutrition 106.2 (2017): 704-705.
  6. Prachayawarakorn, Somkiat, Chonlada Raikham, and Somchart Soponronnarit. "Effects of ripening stage and steaming time on quality attributes of fat free banana snack obtained from drying process including fluidized bed puffing." Journal of food science and technology 53.2 (2016): 946-955.
  7. Ojo, Omorogieva, et al. "The effect of dietary glycaemic index on glycaemia in patients with type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials." Nutrients 10.3 (2018): 373.
  8. Foley, Peter J. "Effect of low carbohydrate diets on insulin resistance and the metabolic syndrome." Current Opinion in Endocrinology, Diabetes, and Obesity 28.5 (2021): 463.
  9. https://lpi.oregonstate.edu/mic/food-beverages/glycemic-index-glycemic-load

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