Diabetes : understanding the low glycaemic diet

Published 13 Dec 2019 • Updated 17 Dec 2019 • By Camille Dauvergne

When you are diabetic, blood sugar levels are very important and are determined by what you eat. The glycaemic index indicates how much of an effect a particular food has on blood sugar levels and is the base of the low-glycaemic ("low-GI") diet. What is the low-GI diet? What are its advantages and limits? Read our explainer guide and leave your opinion in the comments!

Diabetes : understanding the low glycaemic diet

What is the glycaemic index?

The glycaemic index is defined as the speed with which a particular food can alter an individual’s blood sugar level. The glycaemic value of each food is compared against glucose (sugar), the highest value on the index.

The glycaemic index value allows us to classify foods that contain glucose on a scale between 0 and 100, depending on the glucose content. Foods below 55 are considered to be low-GI, medium-GI foods fall between 55 and 70, while high-GI foods are above 70 on the scale. For example, grapefruit is a low-GI food, white rice is a medium-GI food and potatoes have a high rating on the glycaemic index. Blood sugar levels rise more slowly when we eat a grapefruit than when we tuck into a plate of potatoes!

It is important to note that GI is independent of the amount of a particular food we consume and doesn’t apply to foods that are glucose-free.

You can get an idea of what sorts of foods are low, medium or high GI by looking at this Glycaemic Index Table here: Glycaemic Index Table

How does a low-glycaemic diet (“low-GI diet”) work?

When following a low-GI diet, a patient chooses lower-GI foods over higher-GI foods to limit fluctuations in blood sugar levels.

Avoid processed foods

Certain factors can affect a food’s GI value including the form in which it’s consumed (liquid/solid), how it’s cooked and whether it’s high in fibre or fat. In general, it’s better to favour whole foods and avoid over-processed ones, or foods with added sugars like fruit juices, fruit purees, jams, mass-produced white and whole breads and cereals, etc. Industrial heat treatments also raise GI values which is why raw fruits and vegetables, or those home-cooked using steam or boiling, are preferable to baked or fried ones.

A varied and balanced diet

Fibre, protein and fats can help stop or slow down the absorption of glucose and lower a food’s glycaemic index. Eating a balanced diet, one that contains sugars, fats and proteins, can help stabilise blood sugar levels. Of course, portion size also plays a part. 

Physical activity after meals, such as a half-hour brisk walk, will also help to lower one’s blood sugar levels.

What are the limits of a low-GI diet?

One of the principal drawbacks of the low-GI diet is that it doesn’t account for how much of a particular food should be consumed. Even low-IG foods should be eaten in moderation!

Besides that, foods are classified only by their glucose content, which can be problematic for certain foods like eggs, avocadoes or cheese, which are low GI, but high-fat. This concerns type-2 diabetes patients particularly since they generally need to control or lose weight and cut out high-fat foods from their diets.

On the other hand, a low GI diet doesn’t present any particular health-risks as long as a patient continues to take their treatment as directed and keep regular track of their blood sugar levels.

Now that you mentioned it…how are diabetes and diet connected? 

Diabetes, both Type 1 and Type 2, is an auto-immune disease that results from a number of factors. However, being overweight or obese and sedentary are often among the initial causes of diabetes. Diet plays a very important role, both for diabetes prevention and controlling diabetes symptoms. For any individual, a diet plan should assure that they’re getting the nutrients they need, but for diabetic patients, another specific factor comes into play: controlling blood sugar levels. The goal is to avoid hyperglycaemia (high blood sugar) which can cause complications from diabetes to become more severe or longer-lasting.

Furthermore, even if medical treatments can help limit blood sugar, pairing them with a balanced and well-tailored diet is essential to keeping diabetes under control. Another advantage is that many low IG foods are also rich in fibre, which is essential for good digestion

Type 2 Diabetes: a balanced diet can delay insulin resistance

For patients living with Type 2 diabetes, the goal is to increase physical activity and avoid foods containing too much sugar and/or fat. Diet has a very important role is getting diabetes under control, since it is directly responsible for blood sugar levels. When a patient eats something sugary, its absorption by the body causes a spike in glucose levels and the secretion of physiological insulin. When a patient’s diet contains too many high-GI foods, it brings on frequent glucose spikes and excessive insulin secretion. After a certain point, the patient’s cells become desensitised to insulin which can no longer serve its original purpose (glucose reduction) and the patient becomes “insulin resistant”. This is the final stage of diabetes where oral treatments are no longer effective and must be replaced with insulin therapy (injections)

Pre-diabetic: delaying diabetes diagnosis with diet changes

A low-GI diet may also be prescribed for pre-diabetic patients – in the stage just before diabetes. Pre-diabetic patients show high blood glucose levels when tested on an empty stomach, but not high enough to be considered hyperglycaemic. A low-GI diet allows them to keep diabetes at bay for as long as possible.

Warning: This article is a general overview and does not replace medical advice given by a health-care professional. It does not take into account individual patient cases which may vary. Each patient is different, always take your physician before beginning or altering your treatment!

Article written by Louise-B with Camille Dauvergne, 4th-year pharmacy student.

avatar Camille Dauvergne

Author: Camille Dauvergne, Junior Community Manager France

Camille Dauvergne is currently a Junior Community Manager at Carenity. She assists the France Community Manager in animating the platform, easing member navigation of the site and encouraging them to interact.... >> Learn more


on 20/12/2019

While the low GI diet is a way of regulating the speed at which glucose is produced, it does not solve the issues that carbs are still going to turn to sugar eventually.  For the overweight person with Type 2 Diabetes it is the amount of energy that is being consumed that is a big problem.

Unregistered member
on 21/12/2019

I regulate my blood/glucose levels by regulating the amount of carbohydrates that I consume.  I stopped taking sugar in my tea and stopped adding it to any foods some 12 years ago. I even tried the 'Slimming World' diet on direction of my GP, but as I found out that diet 'ain't the one for me', just keep an eye on your carb intake in conjunction with your blood/glucose readings and work out the best regime for YOU. You can try all of these 'fads' and find that you are no better off. My advise is to be vigilant and sort out which foods keep your blood/glucose level manageable. Good luck.

robjmckinney • Ambassador
on 07/01/2020

Processed is not the enemy claimed and the importance of reading labels and understanding the information is essential. Cheap processed food is not full of sugar as it is an expensive ingredient. Most reduced sugar products have in fact higher levels of sugar than cheap processed food. Jam is a perfect example with very expensive reduced sugar version has much higher levels compared to the basic priced jam. Shopping intelligently and reading labels is an essential skill for a diabetic to allow a reasonably normal life. Losing weight is important but 'lest we forget' 50% of type 2 diabetics are thin and age related.

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