Updated 22 April 2013

Carbs debate: the importance of GI

Low-GI foods offer protection from heart disease, lead to improvement in diseases such as diabetes and bring about better weight loss than any other diet, the GI Foundation says.


Legend has it that 200 years ago a large community lived in and around the Mediterranean Sea. This community was very healthy and happy, but ambition obliged them to cross the Atlantic Ocean in an attempt to strive for a more prosperous way of life. Their ambitions and wishes were realised and after a hundred years they became the richest country in the world, but unfortunately their health deteriorated. Their Mediterranean diet changed to a staple diet of hamburgers, ribs, chips and cream in their coffee.  Many people became fat and/or sick, some dying from their new diet.  Heart diseases, cancer and conditions such as diabetes and obesity hit their community hard.

They became aware that saturated fats were responsible for this deterioration and changed their staple diet to include muffins and bagels (refined carbohydrates).  A large selection of sweetened cool drinks was developed to enable the population to slake their thirst.  Meanwhile portion sizes also increased dramatically and even more people quickly became fatter and less healthy.  Some doctors started to wonder if the hamburger and chips diet was not perhaps better than the bagel and Coke diet.

However, there is still a large number of people living in good health around the Mediterranean Sea. Unlike the pioneers who enjoy hamburgers, ribs, chips,  muffins and Coke those who remained behind maintained a diet that had hardly changed in two centuries. They stayed with their traditional diet that consisted of whole grains, no red meat or eggs or chicken, low quantities of low-fat dairy and lots of fish, as well as healthy quantities of olive oil, olives and nuts and lots of vegetables, salads and fruit. They still enjoy the same food they always had and still enjoy very good health. But some doctors still wonder if the hamburger and chips diet is not perhaps better than the bagel and Coke diet.

Glycaemic index

The whole high fat and low carbohydrates debate raises its head every few decades.  But it is now the 21st century and since the introduction of the glycaemic index (GI) in 1981, GI has finally become part of the debate. It brings a whole new perspective to the table. 

Detailed studies have shown that a diet high in high-GI (refined) carbohydrates indeed promotes many illnesses including heart diseases, diabetes, cancer as well as overweight and obesity.

It is for this very reason that lower GI-carbohydrates should be preferred in a daily diet, many of them being staple foods in the Mediterranean diet, namely oats, whole grain bread, brown rice and legumes. 

Low GI-carbohydrates are well known to not raise blood glucose levels too much, to lead to less insulin being produced by the pancreas, lessens pancreatic activity and in so doing helps to prevent diabetes and other life style diseases.

Low GI foods offer protection from heart diseases, lead to improvement in diseases such as diabetes and bring about better weight loss than any other diet.

Mono and poly-unsaturated fats

The Mediterranean diet is not shy of fat, but it consists substantially of mono and poly-unsaturated fats (mainly obtained from omega-3 poly-unsaturated fatty acids).  It has been conclusively proved that when saturated fats in the diet are replaced with mono and poly-unsaturated fats (omega-3 and 6) insulin sensitivity is increased which helps prevent diabetes, reduces dangerous LdL-cholesterol whilst increasing advantageous HdL-cholesterol and prevents heart diseases and drastically reduces the risk of various cancers such as colon cancer.

It has been shown in many studies that a diet high in saturated fat has been coupled with high levels of LdL-cholesterol, weakened functioning of cell membranes and increased risk of heart disease and other life style diseases, including overweight, as well as increased risk of cancer e.g. breast cancer.

No studies show any advantage to the use of saturated fats and in no country’s heart foundation do they recommend the increased intake thereof. 

A matter of balance

Health and nutrition expert Prof Nola Dippenaar suggests that not more than 30% of your total fat intake of 10% of your kilojule intake should be saturated fat. The rest should consist of mono-unsaturated fats (half) and poly-unsaturated fats (half).

In the South African context we should aim to include omega 3 daily, because it is not generally available in our diet and has many advantages, such as protection against Alzheimer’s disease and improvements in concentration and insulin sensitivity (Haag and Dippenaar , 2005), decrease of triglycerides and blood pressure etc.

Healthy diet is a matter of balance and there is general agreement between dieticians and nutritionists that a healthy diet should consist of 50% carbohydrate, 30% fat and 15 – 20% protein.  The energy intake must be balanced by the energy usage otherwise one is liable to become fat regardless of whether the diet is higher in fat or carbohydrates. Most of us also tends take in far too much macro-nutrients and too few micro-nutrients that are obtained from vegetables and fruit.

At least 50% carbs

In my 30 years experience as dietician, I have noticed that it is almost impossible for most people to follow a diet that contains less than 50% carbohydrates.

When skimping on the better foods like slower absorbed carbohydrates, fruits, vegetables, nuts and other good fat and lower fat protein sources they break out only to crave sweets, high fat foods, alcoholic drinks or meat, all the bad stuff. They end up have too little energy to exercise and don’t lose any weight and definitely not fat mass.  (Read case study of marathon athlete Roald.)

Research by Harvard underscores this, that people who consistently choose the less nutritious foods on a consistent basis do indeed pick up weight and increase their risk to the major lifestyle diseases. Read more.  

As soon as they begin eating GI smart, (i.e. low GI when inactive and before exercise, but higher GI during extended periods of exercise), as well as eating fat smart (i.e. lower fat with a focus on healthy fats), their cravings disappear and they have enough energy to exercise and they lose weight and mostly body fat.  This type of diet is much easier to become a life style.  (Read case study of Jacques who lost 50kg in a year.) 

As the Glycaemic Index of SA (GIFSA)  we have tried to capture this healthy, balanced diet pattern with the words “GI Smart – Fat Smart” eating.  With food science development to date it will be irresponsible to ignore the types of carbohydrates (GI) and types of fats.

Written by Liesbet Delport, registered dietician and research manager of the GI Foundation of South Africa 

(References available on request)

- (Health24, April 2012)

(Photo of healthy low-GI foods from Shutterstock)

Read more:

Carbs: the 55% majority winner
Tim Noakes on carbs
Protein vs. carbs: the great debate

To learn more about the Glycaemic Index, visit Health24's Glycaemic Index Centre or the home of the GI Foundation of South Africa


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