Dr Elena Philippou, PhD, RD
28 July 2020 - 4 minute read
Insulin Resistance and Glycaemic Index
Wondering what 'insulin resistance' means and how diet glycaemic index (GI) can help? Read below to find out
Wondering what 'insulin resistance' means and how diet glycaemic index (GI) can help? Read below to find out.
When we consume a food that contains carbohydrates e.g. bread, rice, spaghetti, fruit, sweets, the carbohydrates are broken down by our digestive system into glucose (sugar), which enters the bloodstream.
As blood glucose (sugar) concentration rises, the pancreas produces insulin, a hormone that aids uptake of glucose from the blood into the cells for energy or storage. This uptake leads to a reduction in blood glucose concentration. If blood glucose concentration drops because of fasting for many hours, the pancreas begins to produce glucagon, which signals the liver to start releasing stored glucose. This interaction of insulin and glucagon ensures that cells throughout the body and especially in the brain have a constant supply of sugar.
Healthy carbohydrate metabolism is extremely important but inability to control blood glucose increases the risk of type 2 diabetes, which results from the improper use of glucose and insulin by the body.
Type 2 diabetes usually develops gradually over several years, beginning when muscle and other cells stop responding to insulin. In most cases, but not always, the person has extra weight and especially extra fat in the abdomen, called visceral fat that accumulates around the internal organs. The condition of not responding to insulin, known as insulin resistance, causes high blood sugar (hyperglycemia) and high blood insulin concentrations (hyperinsulinemia) and these concentrations remain high after eating. Over time, overproduction of insulin by pancreatic cells causes damage and is followed by a decrease in insulin production.
Insulin resistance can be diagnosed by simultaneous fasting blood tests of glucose and insulin, which show how much insulin is needed to maintain blood glucose. Insulin resistance also occurs in women with polycystic ovary syndrome where other hormonal disorders may coexist, but also in overweight / obese children. The person feels tired, has a strong feeling of wanting to eat sweets especially after eating and may also have elevated triglycerides, hypertension and depression. Since insulin is an anabolic hormone, the increased concentration causes the accumulation of fat in the abdomen and this in turn causes a vicious cycle of increasing insulin resistance and body weight and fat.
How can diet help?
The best treatment for insulin resistance is weight loss and especially reduction of visceral fat through a diet-exercise combination, and if needed medication. In relation to diet, it is necessary to reduce calories by 500 kcal/day, have regular and stable meal times and choose foods with low glycemic index (GI) and glycemic load (GL).
Glycemic index (GI)
In the past, carbohydrates were divided into 'simple', such as fructose and sugar (sucrose), and 'complex', such as starch. This separation, however, does not take into account the effect of carbohydrates on blood sugar and chronic diseases. To explain how carbohydrate-rich foods affect blood sugar, the Glycemic Index (GI) was proposed in 1981 and is considered the best way to classify carbohydrates, especially starchy foods.
The GI ranks carbohydrates on a scale of 0 to 100 based on how quickly they increase blood glucose concentration following consumption. Foods with a high GI, such as white bread, are quickly digested and cause significant fluctuations in blood sugar. Low GI foods, such as coarse oats, are digested more slowly, causing a gradual rise in blood sugar. This reduces the need for insulin in the blood and so the pancreas does not 'work' as hard as before, resulting in a gradual reduction in insulin resistance.
Examples of low GI foods (GI <=55 on the scale where the GI of glucose is 100) are coarse oats, whole grain seeded breads, bulgur wheat, quinoa, apples and nuts, and high GI foods (GI >=70) include white and brown bread, jasmine rice, baked and fried potatoes and watermelon.
Research has shown that eating high GI foods can lead to an increased risk of type 2 diabetes, heart disease, obesity, age-related macular degeneration and colon cancer. In contrast, low GI foods have been shown to help control type 2 diabetes and improve weight loss. In the book I edited 'The Glycemic Index: Applications in Practice', published by CRC Press 2016, you can find hundreds of studies focusing on GI. The link to the book can be found here: https://www.taylorfrancis.com/books/9781315371764
The glycemic load (GL) of a food is determined by multiplying its glycemic index by the amount of carbohydrates it contains. Generally, a GL of 20 or greater is high, 11 to 19 is average, and 10 or less is low. Using GL, you can choose low GI foods in the right amount to avoid fluctuations in blood sugar and insulin.
Below are some examples:
Low glycemic load (10 or less):
Medium glycemic load (11-19)
Whole grain rice Basmati: 1/4 cup cooked
Multigrain seeded bread: 1 slice
Wholemeal pasta: 1 1/4 cup cooked
Sweet potato: 90 g cooked
High glycemic load (20+)
Processed Breakfast cereals: 30 gr
Cous cous: 1 cup cooked
White rice: 1 cup cooked
If you have insulin resistance, polycystic ovary syndrome, type 2 diabetes or other related problems, choose low GI and low GL foods. We can help you with personalized tips and a diet plan.