A comprehensive study of 40,000 Australians over 17 years found low-carbohydrate, high-fat diets increased a person's chances of developing diabetes by 20%.
The researchers from RMIT University and Monash University say the study is the first to look at the long-term effects of a low carbohydrate diet on chronic diseases using Australian data.
The study, led by Distinguished Professor Barbora de Courten with PhD scholar Robel Kabthymer, is published in the journal Diabetes and Metabolic Syndrome: Clinical Research and Reviews.
De Courten, who holds positions at both institutions, said one in 20 Australians had diabetes, and perhaps even more because of undiagnosed diabetes.
The study used data from about 40,000 Melburnians, aged 40-69, recruited into the Melbourne Collaborative Cohort Study (MCCS) between 1990 and 1994. Their health was then reviewed in 1995-1998 and 2003-2007.
The RMIT and Monash team analysed the percentage of carbohydrates in the diet and related it to the risk of developing type 2 diabetes later in life.
The Low Carbohydrate Score (LCD) was calculated at the start of the study as the percentage of energy from carbohydrates, fats and protein. The higher the score the less percentage of carbohydrates contributed to energy intake.
The study found that those whose diet included 38 per cent of carbohydrates had a 20 per cent increased risk of developing type 2 diabetes compared to those whose diet included 55 per cent of carbohydrates.
The researchers say this increased risk of diabetes is due to increased incidence of obesity.
Distinguished Professor Barbora de Courten from RMIT and Monash. Credit: Supplied
Why is a low-carb diet unhealthy and how does it lead to diabetes?
When a person eats a low-carbohydrate diet, they need to replace the carbohydrates with other nutrients.
"What we found in our study is that people replaced carbohydrates with unhealthy saturated fats which caused weight gain and type 2 diabetes," de Courten said.
"Eating food high in saturated fats can lead to weight gain but we know they also lead to insulin resistance which is one of the causes of type 2 diabetes independently of weight gain."
Is a low-carb diet suitable in certain circumstances?
If a person had type 2 diabetes, eating a low-carbohydrate diet with unsaturated fats and sufficient protein could have a place, de Courten said.
"But you should always seek advice from your doctor before you make any changes like this to your diet," said de Courten, who is a specialist physician at Monash Health treating patients with diabetes.
The people who were a part of this study did not have diabetes when they started the study, so they were generally healthy.
"For people who don't have diabetes, a balanced diet is the best choice," de Courten said.
"We need to remember that not all carbohydrates are equal. The kind of carbs you want avoid are refined sugars such as soft drinks, juices, white rice, white bread and replace them with unprocessed carbs rich in fibre like grains, brown rice and legumes.
"And eat more of healthy mono- and poly-unsaturated fats such as avocados, nuts, olive oil and fatty fish like salmon."
How can you improve your diet?
People should have balanced diet with minimally processed carbohydrates rich in fibre such as grains, healthy mono- and poly-unsaturated fats with sufficient protein intake from fish and seafood, white meat and legumes, de Courten said.
"The best example of this kind of diet is a Mediterranean diet," she said.
"It goes without saying, if you want to prevent type 2 diabetes then regular exercise, getting sufficient sleep, reducing stress, avoiding alcohol and smoking and maintaining lively social connections are the way to go."
The research paper, 'Association of low carbohydrate diet score with the risk of type 2 diabetes in an Australian population: A longitudinal study' (DOI: 10.1016/j.dsx.2024.103049) is published in Diabetes and Metabolic Syndrome: Clinical Research and Reviews.
