How the glycemic index has changed the meaning of healthy food

Lifestyle diseases have rocketed to epidemic levels in recent times – one Australian develops type 2 diabetes every five minutes, according to Diabetes Australia.

Could we delay or dodge these diseases – and prevent complications for people living with type 2 diabetes – simply by changing our diet and following a healthy lifestyle, with regular exercise?

The University’s Charles Perkins Centre and a University of Sydney spin-off not-for-profit The Glycemic Index Foundation have spearheaded a paradigm shift in approaches to healthy eating and lifestyle diseases that could motivate many people worldwide to change how they choose carbohydrate foods – cereal foods in particular.

Professor of Human Nutrition, Jennie Brand-Miller, has been a leading contributor to several world-first studies that have advanced the Glycemic Index (GI) – which ranks carbohydrates in foods according to how they affect blood glucose levels – from scientific theory to practice.

Her findings are significant because they show the world for the first time how we can use the GI to have a positive impact on weight control, type 2 diabetes and cardiovascular disease, and even diabetes prevention.

The landmark PREVIEW Study was the first type 2 diabetes prevention study to use total diet replacements (Cambridge Weight Plan®) for the weight loss phase.  Participants who consumed four shakes a day – formulated to give them everything they needed – lost an average of 11 percent of their overall body weight in just eight weeks.

Over the following three-year weight loss maintenance phase, the PREVIEW team found that both higher protein/low GI diets as well as conventional healthy diets – combined with exercise and behavioural therapy – produced remarkable weight control.  

The study’s other important conclusion was that we can delay or even dodge type 2 diabetes, because such significant weight loss appears to stimulate stem cell production and reboot the beta cells that produce insulin. The body then returns naturally to more effective control of blood glucose (blood sugar) levels.

PREVIEW complements and reinforces the findings of another world-first study – a clinical trial by Professor Brand-Miller and her team that investigated how people who already had type 2 diabetes would react to a low-GI diet. The results showed that the diet improved average blood glucose levels, a key biomarker that predicts complications in type 2 diabetes.

“The trial meant that the low GI diet worked in practice,” explains Professor Brand-Miller, and that people with diabetes could simply be more selective with the carbohydrates they chose to eat.

After the success of this trial the team began to investigate other applications of the GI and its effect on weight control and cardiovascular disease.

“We saw that blood glucose levels were going up and down in concert with insulin levels, which is a master hormone that drives fat synthesis,” says Professor Brand-Miller. “I think because we applied the GI to weight and appetite control, it became a much more interesting subject.”

Recent research suggested 12-month old infants of mothers who had consumed a high GI diet during pregnancy had higher risk of cardiovascular disease. Thus blood glucose levels in mothers were playing a role in atherosclerosis (hardening of arteries) in the second generation.

Her research in this field, which links high blood glucose levels with harmful effects in many different ways, is yet another of her game-changing discoveries that will have far-reaching implications for our diet, health and disease for generations to come.

The Glycemic Index Foundation will soon go one practical step further by launching a new profit – for – purpose venture, a bold and disruptive social enterprise whose aim is to provide funding for Diabetes prevention and community education programs.