If you’ve been searching for information on how to eat a healthy diet or lose weight, you’ve probably come across the Glycemic Index. This article is designed to clear up any confusion about what the GI means, and how you can apply it to creating a more healthy diet.


What is the Glycemic Index?

The glycemic index is a way of rating the effects of different carbohydrate-containing foods on a person’s blood sugar levels in the hours after they have eaten. It was designed for people with diabetes, to help regulate their blood sugar levels.

Foods which are high on the glycemic index (70-100) are quickly digested and absorbed into the bloodstream, causing a rapid spike in blood sugar levels. This includes anything sugary, and processed carbohydrates such as white rice and white bread. These are broken down rapidly into glucose so it doesn’t take long for them to hit your bloodstream, giving you a sugar high that quickly fades.

On the other end of the spectrum, foods low on the glycemic index (0-55) include pulses (lentils, beans), and wholegrains. Once inside the body these types of food are digested more slowly, causing a gentler rise in blood sugar levels and a more sustained source of energy.

You can find the GI value of certain foods using databases such as this one. The government has also published a document listing the GI values of many common foods.


Why is this important?

Meals made mostly of low-GI foods release their energy more slowly into the bloodstream. This makes you feel full for longer, and keeps up your energy levels. This may help to maintain a healthy weight by preventing food cravings.

Low GI diets have been shown to have several additional health benefits, such as reducing the risks of Type 2 diabetes and heart disease. In people who are already diabetic, eating low-GI foods has been shown to help manage blood glucose levels in some patients with Type 2 diabetes.


Is eating only low-GI foods healthier?

It’s important to exercise caution as relying on the glycemic index to tell you which food is healthiest can be a mistake.

Some foods, like wholegrains, vegetables and pulses are both low GI and healthy. But some unhealthy options are low on the GI index too- like chocolate cake. This is because foods containing fat or protein slow down the absorption of carbohydrates, lowering the GI ranking.

As well as this, some foods are not unhealthy when eaten as part of a balanced diet but still rank highly on the GI index, such as many starchy root vegetables like parsnips and beetroot, and fruits such as bananas.

The GI number of different food is also not fixed, and will depend on how you prepare certain foods. For instance, bread with butter has a lower GI than bread eaten alone, as you’re adding in fat.

These facts mean the GI index is just one part of what you should consider when deciding on healthy food choices. It’s important to look at other aspects such as the fat and calorie content of the food. If you only choose food based on its low GI values you might end up consuming an unhealthy diet too high in fat, calories, salt and sugar.


What else is important for making healthy dietary choices?

Rather than just focusing on the GI of specific foods, it may be useful to look at the bigger picture of what you’re eating. The NHS publishes an Eatwell Guide which shows the proportions of different food types you should aim to include in your diet. These guidelines include:

  • Including a variety of fruit and vegetables in your diet
  • Choosing higher fibre, wholegrain carbohydrates
  • Avoiding excess sugar and salt
  • Eating less foods containing saturated fat (whole milk, cream, butter, red meat), and choosing low-fat dairy options.

For more information on healthy eating, here’s 8 practical tips for getting your diet sorted. If you’re concerned about your diet or want to discuss whether changing your diet could help maintain a healthy weight, you can book a GP appointment.