By Jewel Topsfield and Henrietta Cook
It’s credited with quick weight loss and endorsed by celebrities such as Kim Kardashian, but researchers say a low-carbohydrate diet can increase a person’s risk of developing diabetes by 20 per cent.
The research – conducted by a team from Monash and RMIT universities and involving 40,000 Melburnians over 17 years – is the first to look at the long-term effects of a low-carb diet on chronic diseases using Australian data.
Professor Barbora de Courten Credit: Simon Schluter
It revealed that a low-carb diet intake increased the long-term risk of type 2 diabetes through obesity, possibly due to eating more fats and foods low in fibre.
“We found that people who reduce their carbohydrates tend to replace them with unhealthy fats which contributes to gaining weight and puts them at a higher risk of developing diabetes,” said lead researcher Distinguished Professor Barbora de Courten.
Nearly 1.3 million Australians – one in 20 people – were predicted to have diabetes in 2020, although the real figure is expected to be higher because of undiagnosed disease. The number of Australians living with the chronic condition almost tripled between 2000 and 2021, according to the Australian Institute of Health and Welfare.
“We know that high-carbohydrate diets, that are highly processed, low in fibre, and rich in refined sugars can lead to weight gain. Furthermore, the highly refined carbohydrates can lead to type 2 diabetes,” she said.
“But studies to date have only focused on examining low-carbohydrates for managing existing type 2 diabetes.”
The study – published in the journal Diabetes and Metabolic Syndrome: Clinical Research and Reviews – said while research suggested that low-carbohydrate diets were more effective for quick weight loss, little was known about their long-term effect on the risk of chronic disease.
The researchers recruited 40,000 Melburnians – aged 40 to 69 – between 1990 and 1994.
The participants’ health was reviewed three times during this time period, with almost 26,000 participants still involved at the end of the 17-year trial, conducted in collaboration with Cancer Council.
The team analysed the percentage of carbohydrates in the diet and related it to the risk of developing type 2 diabetes later in life.
It found that those whose diet consisted of 38 per cent carbohydrates had a 20 per cent increased risk of developing type 2 diabetes – even when adjusted for obesity – compared with those whose diet included 55 per cent of carbohydrates.
Jane Robinson, a dietitian and education program manager at Diabetes Victoria, said the research was a valuable addition to the carb-fat debate.
“Whilst the findings of this study are interesting, this study focused on the total amount of carbohydrate that people were eating, it did not examine the types of actual foods that people were eating to make up a lower or higher carbohydrate intake,” Robinson said.
“By reducing the amount of carbohydrate in the diet, there is likely to be an increase in fat consumption, which can lead to weight gain and hence diabetes risk, as witnessed in this study.
“Eating fewer carbohydrate foods also reduces the intake of wholegrains, fruit and dairy products, which may be protective in developing type 2 diabetes.”
Robinson said recommendations to reduce the risk of type 2 diabetes included increasing healthy fats, wholegrains, dairy foods, fruits and vegetables, while reducing saturated fats and refined grains and limiting fat, sugar and salt, including processed meats and sugary drinks.
Kevin Edwardes was diagnosed with pre-diabetes in his early 20s and advised by a dietitian to cut out carbohydrates from his diet and increase his intake of saturated fats.
“I was actively encouraged to eat bacon, more chicken,” Edwardes, now 59, said.
The teacher from Cheltenham in Melbourne’s south-east said he put on weight following this advice and was diagnosed with type 2 diabetes in his mid-20s. He received similar advice in his mid-40s.
Edwardes is now dependent on insulin. He is unsure whether the advice he received about a low-carbohydrate diet and saturated fats sped up his development of diabetes.
“Everyone says what they think is best practice based on what they believe at the time,” he said.
“I hope the GPs and dietitians are keeping up to date with the latest research.”
Start the day with a summary of the day’s most important and interesting stories, analysis and insights. Sign up for our Morning Edition newsletter.