The study team found that people following a ketogenic diet for three months saw significant improvement in their blood sugar control.
Average blood sugar control
"A five to 10% carbohydrate diet over three months led to a remarkable reduction in haemoglobin A1c levels," said study author Dr Angati Kanchana Lakshmi Prasana. Kanchana is a consultant biochemist at CARE Hospitals in Visakhpatnam, India.
Haemoglobin A1c is a blood test that estimates average blood sugar control over the past two to three months. In general, people with diabetes are advised to have an A1c level of 7% or lower.
It's still up for debate whether it's this specific diet that causes improvement, eating fewer carbohydrates or simply the fact that people lose weight on the diet.
Dr Genevieve Lama is an endocrinologist at New York-Presbyterian Medical Group Hudson Valley in New York. She said that when people lose weight, their blood sugar levels go down. And it doesn't take a huge weight loss to make a difference. She said losing just 5% of your weight has an impact on blood sugar levels.
Plus, a low-carbohydrate diet is known to reduce blood sugar levels, she said.
During digestion, carbohydrates are broken down into simple sugars. The hormone insulin allows the body's cells to use this sugar for fuel.
A big change in lifestyle
In type 2 diabetes, however, the cells aren't as sensitive to insulin. That means more insulin is needed to do the same job. But sometimes the body can't keep up. If that happens, blood sugar levels rise.
Certain foods – such as processed simple carbohydrates like white bread, sweets and sugar-sweetened beverages – quickly raise blood sugar, according to the American Diabetes Association. That's why a diet that limits these foods can help manage blood sugar levels.
The ketogenic (keto) diet was originally designed as a treatment for people with the seizure disorder epilepsy. It typically allows 50 grams of carbohydrate or less a day, according to the Academy of Nutrition and Dietetics.
On a keto diet, people often don't have grains, breads or cereals. Often, even fruits and vegetables are restricted. The diet requires a big change in lifestyle.
The latest study recruited 130 people with type 2 diabetes to follow a ketogenic diet for 12 weeks. There was no control group for comparison.
Study volunteers were between 35 and 60 years old. About one-third were female.
Very limited diet
Average weight loss was between 15 and 22 pounds (about 6 to 10kg). Before the diet, the study volunteers were slightly overweight. Afterwards, they fell in the normal weight category, on average.
The diet was very limited, with a maximum of 20 grams of carbohydrates a day, Kanchana said. (For reference, one slice of bread is 15 grams and a cup of broccoli has 6 grams of carbs, the US Department of Agriculture says.)
Typically, the Indian diet is carb-laden, with around 300 to 400 grams of carbohydrate daily, Kanchana said. In some areas of India, people consume a lot of wheat products. In others, the diet contains more rice products.
The study diet contained fats like coconut oil and butter, animal products like chicken, eggs, lamb and pork, dairy products, green leafy vegetables and other green vegetables. The diet avoided root vegetables like potatoes and carrots, Kanchana said.
Daily calorie counts were about 1 500 to 2 000 calories a day.
The average haemoglobin A1C dropped from 7.8% to 6.4% after three months on the diet. Mild constipation was the only adverse effect.
Increased risk of heart disease
However, more than 10% of the study participants (15 people) dropped out of the study. Kanchana said culturally it was difficult for some people to maintain the carbohydrate restrictions. Economic reasons may have prompted others to stop. It's more expensive to purchase healthy fats and animal products than processed carbohydrates, she noted.
There is also concern that a diet high in fat and animal products might increase the risk of heart disease. Kanchana said the long-term effects of the diet need to be studied.
Diabetes doctor Lama said she thinks this diet would be difficult to maintain for a long time because it's so restrictive. And she has concerns about the high fat in the diet, as well as the loss of certain healthy carbohydrates.
"I generally tell my patients to eat low carb, but not no carb. And to get a feel for what they think they can maintain as their lifestyle. If you can't maintain it, it really just makes you feel defeated. It's more realistic to lose weight gradually and keep it off," she said.
She recommends keeping a food log before you see a dietitian, so you can work with the dietitian and come up with a healthy eating plan that has lots of foods you enjoy.
The study was to be presented at the American Association for Clinical Chemistry annual meeting in Anaheim, California. Findings presented at meetings are typically viewed as preliminary until they're published in a peer-reviewed journal.
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