Your guide to low Gl diet

Low glycemic index (GI) diet has long been applauded with its benefits in blood sugar and weight management. Is it a myth or science-based?

Glycaemic lndex 101

GI generally tells how rapid and high the blood sugar level raises after eating a food item containing carbohydrates content. The faster the carbohydrate content. The faster the carbohydrate digestion and absorption, the faster the blood sugar would rise, giving a higher GI value or vice versa. Each food item gas their unique due to the difference in ability to rise blood sugar level, which is defined as high GI, GI value of 70, moderate for 56-91 and low for 55 or below.

What’s good about it?

Apart from greater satiety with low GI foods for weight management, enjoying diet with low GI foods has been linked to improvement of blood sugar management among diabetic people to stay away from diabetic complications such as cardiovascular disease, stroke and kidney failure.

Factors interfering GI of a food

To make things more complicated, GI of a food can be interfered by numerous factors. The form of starch, amylose and amylopectin content, in a food determines the rate of digestion. Due to structural difference, amylopectin is easier to digest than amylose. As a result, glutinous rice, containing more amylopectin than plain rice, has higher GI value. The degree of processing also alters particle size and in turn, affects the GI. It is expected red bean paste has grater GI value than red bean. Congee has higher GI value than cooked rice because the longer duration of cooking makes food easier to get digested and absorbed. Given that fruit maturity does alter GI value, it is not surprising that sweet ripe banana has higher GI than unripe one. Interestingly, the advice, ‘Eating a whole fruit is better than juice,’ you always hared of is partly due to the GI value as well. Dietary fiber, fat and acidity, via slowing down digestion process and stomach emptying. Lower GI of a food, so enjoying a whole fruit benefits from higher fibre content resulting in lower GI than juice.

Low GI food = Healthier option?

Not necessarily true. As mentioned, now GI food can be sometimes high in fat, just like pork knuckle rich in saturated fat. Eating too much of it can lead not only to weight garn, but also high ‘bad’ (LDL) cholesterol. Loading too much of low GI food can also contribute to excessive carbohydrate intake eventually rocket the blood sugar level. Stay wise on low GI foods!

Embracing the benefits from low GI foods is not a rocket science. Embracing a healthy diet ‘3 lows 1 high’-now fat sugar and salt whine high fibre, together with less processed food choices, allow us to incorporate low GI concept into our diet routine to safeguard our health.


  1. Atkinson FS, Foster-Powell K, Brand-Miller JC, International tables of glycemic index and glycemic load values: 2008. Diabetes Care. 2008;31:2281-3.
  2. Jenkins DJ, Kendall CW, Mckeown-Eyssen G, Josse RG, Silverbeing J, Booth GL, et al. Effect of a Low-glycemic index or a high-cereal fiber diet on type 2 diabetes: a randomized trial. JAMA. 2008;3002742-53.

330 Tips provided by:  Ms Grace Lam  (Senior Dietitian - Centre for Nutritional Studies, School of Public Health and Primary Care, Faculty of Medicine, CUHK)

Date: 2016-12-01