The low GI diet is based around the glycemic index (GI) – a ranking system used to measure food’s impact on blood sugar levels. Simply put, the lower the GI rating, the more steady the impact on blood sugar.

Research has shown that eating a low GI diet can offer a number of health benefits; including weight loss, lower blood sugar levels, and a reduced risk of heart disease and type 2 diabetes.

However, experts also warn against relying on the GI value of foods alone. This is because there are also a number of other factors, such as cooking method and nutrient composition, that affect the health value of food.

Here, we’ll cover exactly what glycemic index is, what a low GI diet looks like, and what some of the benefits and shortfalls are.

What is the glycemic index (GI)?

What is the glycemic index

Carbohydrates, such as those found in bread, cereals, dairy products, fruits, and vegetables, are an essential part of any healthy diet.

When we eat carbohydrates, our digestive system breaks them down into simple sugar, which then enters the bloodstream. However, not all carbohydrates are the same, and therefore have different effects on blood sugar.

The glycemic index (GI) is a measurement system used to rank carbohydrate-containing foods according to how quickly they affect blood sugar levels. The lower a food’s GI rating, the more stable its impact on blood sugar levels.

To determine a food’s GI rating, experts look at how quickly it’s broken down and absorbed into the bloodstream, compared with 50g of pure glucose – which has a GI value of 100.

The three GI ratings are…

  • Low GI: 55 or lower

  • Medium GI: 56-69

  • High GI: 70 or higher

Food with a low GI value is digested and absorbed more slowly, which causes smaller, steadier rises in blood sugar levels. High GI foods, on the other hand, are digested and absorbed quickly, which causes rapid spikes and falls in blood sugar levels.

Low GI foods can be preferable for a number of health reasons, including the fact that quick blood sugar spikes can lead to fatigue and lethargy, and in the long-term, increase the risk of conditions like type 2 diabetes.

However, it’s important to note that only carbohydrate-containing foods are given GI value – so those with no carbohydrate content won’t be found on GI lists. Examples of these foods include chicken, beef, fish, eggs, herbs, and spices.

What are some examples of high GI and low GI foods?

What are some examples of high GI and low GI foods

The low GI diet essentially involves swapping high GI foods for low GI alternatives.

There are plenty of delicious and healthy low GI foods to choose from, such as…

  • Whole grain, rye, multigrain, or sourdough bread

  • Fruit including strawberries, apples, peaches, apricots, plums, kiwi, tomatoes, and more

  • Vegetables including broccoli, carrots, cauliflower, zucchini, celery, and more

  • Starchy vegetables like sweet potatoes, butternut squash, and corn

  • Breakfast cereals such as bran flakes and steel-cut oats

  • Legumes including chickpeas, lentils, butter beans, baked beans, kidney beans, and more

  • Long grain, basmati, and brown rice

  • Grains like barley, quinoa, buckwheat, and more

  • Dairy or dairy replacement products like milk, cheese, yoghurt, soy milk, coconut milk, and almond milk

Other foods that contain little or no carbohydrates (and therefore don’t have a GI value) can also be included in the low GI diet. Some examples include…

  • Fish and seafood such as salmon, tuna, trout, and sardines

  • Nuts like almonds, cashews, walnuts, and pistachios

  • Fats and oil like avocado and olive oil

  • Herbs and spices such as garlic, dill, basil, salt, and pepper

Meanwhile, high GI foods that are avoided in a low GI diet include sugary foods, sugary drinks, white bread, potatoes, and white rice.

For more in-depth guidance on what foods can be eaten on a low GI diet, check out this guide from Low GI Health.

What are the health benefits of the low GI diet?

What are the health benefits of the low GI diet

Some of the top health benefits of the low GI diet include…

1. The low GI diet can be beneficial for diabetes

Diabetes is a condition where the body is unable to process sugars effectively – making it difficult to maintain healthy blood sugar levels.

Experts have suggested that following a low GI diet can be an effective way to manage carbohydrate intake and help to delay or prevent potential complications from type 2 diabetes – including stroke, heart disease, and damage to the kidneys and nerves.

For example, this scientific review revealed that a low GI diet reduced markers of healthy blood sugar control, body weight, and resting blood sugar levels in people with prediabetes or diabetes.

In contrast, research has linked high GI diets with an increased risk of developing type 2 diabetes. In this study of over 205,000 people, those whose diets contained the most high GI foods were found to have up to a 33% greater risk of developing type 2 diabetes than those with the lowest GI diets.

2. Low GI diets may reduce the risk of heart disease

Research has revealed a strong link between high GI diets and an increased risk of heart disease; while low GI diets are associated with a reduced risk.

Having high cholesterol is a risk factor for heart disease and this study found that low GI diets reduced total cholesterol by 9.6% and LDL (bad) cholesterol by 8.6%.

As a result, another study (which tracked 138,000 people for 9.5 years) found that those who ate a low GI diet were less likely to suffer from heart disease and stroke.

3. Low GI diets may promote healthy weight loss

Some research has suggested that low GI diets may promote healthy weight loss.

For example, this study looked at the potential benefits of low GI diets on body mass index (BMI), waist circumference, and waist-to-hip ratio in patients with coronary heart disease.

During the study, one group ate low GI foods and excluded high GI foods, but continued with their usual consumption of fat and protein. The other group followed a routine diet recommended for coronary heart disease which limited fat, fried foods, and some proteins, including whole milk, meat, cheese, and egg yolks.

After three months on the diets, all body measurements within both groups had decreased, but the changes were only significant in the low GI group. Waist circumference, for example, reduced by 9cm in the low GI group, compared with 3.3cm in the routine diet group.

These results can partially be explained by the fact that, because low GI foods take longer to be broken down and absorbed, they can help you to feel fuller for longer. Many people find that this helps to encourage portion control and avoid overeating.

In fact, one study found that eating a low GI breakfast resulted in a decreased energy intake of 285 calories at lunchtime because participants felt fuller for longer.

4. Low GI diets may boost energy and mood

Low GI foods can have a positive impact on energy levels because they release sugar into the bloodstream gradually – providing the body with a sustained, longer-lasting source of energy.

For example, white bread releases four times as much sugar into the bloodstream than hummus (which is made mostly from chickpeas), despite containing the same amount of carbohydrates.

The GI value of foods has been found to impact mood too. As shown in this study, which tracked both overweight people and moderate-weight people, eating a high GI diet resulted in a 38% higher score of depressive symptoms and a 26% higher score for fatigue and lack of motivation.

Those with obesity were also found to have 40% higher depression scores than those of a moderate weight.

5. Low GI diets may reduce the risk of cancer

There’s evidence to suggest that people who eat higher amounts of high GI foods have a greater risk of developing various types of cancer; including breast, pancreatic, colorectal, thyroid, gastric, and endometrial.

For example, this study found that of 1,011 patients with advanced colon cancer, those who ate the most GI foods were nearly twice as likely to see their cancer return. High GI diets have also been shown to increase levels of insulin-related growth factors, which are major risk factors for breast cancer.

Meanwhile, low GI diets have been linked with a reduced risk of breast, ovarian, colorectal, and endometrial cancers.

However, as researchers have pointed out, many high GI foods, such as biscuits, brioches, and ice cream, also contain other ingredients that are known to increase cancer risk – including saturated fats.

What are some disadvantages of the low GI diet?

What are some disadvantages of the low GI diet

Despite the many benefits of the low GI diet, there are some potential downsides to consider.

The key, overrarching issue is that it’s not accurate to assume that all low GI foods are automatically healthy and all high GI foods are unhealthy. For example, watermelon and parsnips are generally classed as high GI foods, while chocolate cake has a lower GI value.

Therefore, here are a number of other factors to consider when it comes to determining the health value of food…

From research, we know that when foods either contain or are cooked with protein and fat, it slows down the absorption of carbohydrates – therefore lowering the GI value.

For example, crisps have a lower GI value than potatoes which are cooked without fat. But, because crisps are high in fat, they wouldn’t necessarily be considered the healthier option, and should only be eaten in moderation.

Other factors, such as how refined foods are, the type of sugar they contain, the amount of carbs you eat in one sitting, and the ripeness of fruit and vegetables, can also have an influence on GI value. For example, comparative research shows that an unripe banana has a GI of 30, while an overripe banana has a GI of 48.

These varying factors mean that while GI food rankings can be useful for promoting healthy dietary choices, they shouldn’t necessarily be relied on as the sole basis or guidance for a healthy diet.

Final thoughts…

As research has shown, eating a low GI diet offers a number of potential benefits – including for blood sugar regulation, healthy weight loss, and mood.

That being said, there are also a number of drawbacks that should be considered. This includes the fact that the GI ratings don’t take into account various other factors, such as portion size, cooking method, and fat content, which also help to determine how healthy foods are.

Therefore, low GI food ratings can be a useful tool for health but shouldn’t necessarily steer the direction of everything you eat. It’s also important to speak to your doctor or another health professional before starting any new diet.

For more healthy diet tips, head over to the diet and nutrition section of our website. Here you’ll find everything from essential vitamin and mineral guides to ideas for healthy lifestyle swaps.