What is glycaemic index and how it helps you make healthier food choices?

Ahead of World Diabetes Day 2025, experts say GI awareness supports better glucose control and smarter meal planning

When you choose what to eat, you probably consider calories or nutrients. But the effect on our blood-sugar levels is often overlooked. Spike or slide in sugar levels matter significantly, especially if you’re managing diabetes or simply trying to maintain stable energy.

 

One useful tool for understanding how different foods impact blood sugar is the Glycaemic Index (GI). In simple terms, it’s a ranking of how quickly carbohydrate-containing foods raise blood glucose, which can help you make smarter food choices.

What is the glycaemic index?

 

The glycaemic index is basically a numerical ranking system with 0 to 100 assigned to a food to measure how fast it can raise blood glucose levels, shares Dr Amitabha Saha, consultant, Critical Care Unit, Medica Superspeciality Hospital, Kolkata.

 

 

"Food with high GI markers gets digested and absorbed quickly in the body causing a sharp rise in blood sugar. Low GI foods generally take more time to get digested," he says.

 

Several factors affect the GI of a food like how ripe it is, how it is cooked, how processed it is along with its fibre/protein/fat content.

There are the three GI ratings:

Low: 55 or less

Include apples, bananas, barley, broccoli, carrots, chickpeas, cashews, dark chocolate, plain yoghurt, milk (skim and whole), mangoes, oranges, pears, strawberries, tomatoes, peanuts, lettuce, peppers, lemons, limes, and eggplant.

Medium: 56–69

These include brown rice, couscous, sweet potatoes, pineapple, popcorn, potato chips, and soda.

High: 70 or above

Examples include white bread, cereals, doughnuts, French fries, pretzels, mashed potatoes, pizza, fried chicken, cheeseburgers, corn chips, and sports drinks.  ALSO READ | Can the '2 per 20' rule really help stabilise blood sugar without exercise?

Why does the GI matter?

Understanding GI matters because your blood sugar levels aren’t just impacted by how much you eat but also about how fast the carbohydrates turn into glucose. 

"GI is a valuable tool for understanding how different foods affect blood-sugar levels, and maintaining healthy blood-sugar levels is essential for preventing long-term health complications such as heart disease, kidney disease, and nerve damage," says Dr Sumaiya Petiwala, a Bangalore-based dietitian and physician.

 

She adds, "For individuals with diabetes or prediabetes, managing blood sugar is even more critical, as their bodies either don’t produce enough insulin or can’t use it effectively. Rapid spikes in blood glucose can lead to hyperglycaemia, which, over time, can cause significant health issues."

 

A diet high in high-GI foods may lead to rapid sugar spikes, which over time can increase the risk of insulin resistance, type 2 diabetes and weight gain.

Conversely, choosing more low-GI foods can help maintain more stable blood sugar levels, support weight management and reduce the metabolic load on your system.

Putting GI into practice

• Replace white rice with whole grains like barley, millets, quinoa or brown rice and white bread with whole grain bread.
• Choose pulses and legumes (chana, moong, rajma), fruits like guava or apple, and non-starchy vegetables such as okra, bottle gourd or spinach.
• Be mindful of cooking methods: for example pasta cooked al dente has a lower GI than when overcooked; similarly, more processed foods tend to have higher GI.
• Pair high-GI foods with foods rich in fiber, healthy fats, and protein. This slows down digestion and reduces the glucose spike.
• Even with low-GI foods, be mindful of portion sizes to manage the overall glycaemic load (GL factors in the number of carbs in a serving of a food to determine how it may affect blood sugar levels)

 

"The focus should be to prioritise food with a lower glycaemic index and balanced nutritional profile while eating small portions," says Dr Saha. 

Also Read: Tired, hungry and gaining weight? Insulin resistance could be to blame

World Diabetes Day 2025

 

World Diabetes Day is celebrated every year on 14 November. This year’s theme, 'Diabetes across life stages', emphasises that diabetes can affect people from childhood through older age and that prevention and care should span the entire life-course.

 

Understanding and using tools like the glycaemic index, paying attention to the quality of carbohydrates and their impact on blood sugar can support better long-term health, particularly for people living with, or at risk of, diabetes.

 

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This report is for informational purposes only and is not a substitute for professional medical advice.