Being overweight and obese are significant risk factors for developing type 2 diabetes. While losing weight can optimize blood sugar levels and reduce the dosage of prescribed antidiabetic drugs, weight loss can be challenging to achieve and maintain. In a new study, Chinese researchers examined the effect that intermittent fasting utilizing a 5:2 diet had on blood sugar control in overweight type 2 diabetics.
The 5:2 intermittent fasting diet involves eating normally for five days and fasting for two nonconsecutive days by eating a quarter of the usual energy intake. Popularized by the late medical journalist Dr Michael Mosley, many find the diet appealing because of its flexibility; it doesn’t matter which two days are ‘fasting days’ as long as they’re not consecutive.
The researchers recruited 405 adults aged 18 to 65 who’d been diagnosed with type 2 diabetes in the preceding year and had not used antidiabetic medications in the past three months. The participants, of which 34.6% were women, had an average body mass index (BMI) of 29.5, meaning they were overweight, and an average HbA1c of 7.9%. HbA1c, or glycated hemoglobin, is a blood test that shows a person’s average blood sugar levels for the last two to three months. The normal range is between 4% and 5.6%.
Participants were randomly assigned to receive antidiabetic medications metformin (Glucophage) or empagliflozin (Jardiance) or to follow the 5:2 diet for 16 weeks. The primary outcome was an improvement of HbA1c from baseline. Secondary outcomes included changes in weight, blood pressure, fasting blood sugar level, fasting insulin level, blood fats (lipids) and cholesterol.
At week 16, study participants in the 5:2 diet group showed the greatest reduction in HbA1c, a drop of 1.9% (so, from the mean value of 7.9%, it fell to 6%). This was significantly greater than the effect of metformin (–1.6%) and empagliflozin (–1.5%). Fasting blood sugar levels in the diet intervention group also decreased. At the end of an eight-week follow-up, 76.6% of participants in the 5:2 diet group maintained an HbA1c of less than 6.5%.
Additionally, at week 16, those on the 5:2 diet showed greater weight loss (–9.7 kg/21.4 lb) compared to metformin (–5.5 kg/12.1 lb) and empagliflozin (–5.8 kg/12.8 lb). And, compared to the antidiabetic drugs, the diet intervention produced a significant reduction in waist and hip circumference, blood pressure, and blood lipids.
In the 5:2 diet group, one participant experienced constipation, and 5.9% of participants had symptoms of low blood sugar (hypoglycemia). In the metformin group, 6% had hypoglycemia and 19.4% mild gastrointestinal symptoms. In the empagliflozin group, 3.7% experienced hypoglycemia, 2.2% urinary symptoms, and one participant reported being thirsty. Two participants on empagliflozin reported serious adverse events, including severe rash and hospitalization due to elevated blood ketones, which resolved with treatment.
“We found that among Chinese adults with overweight or obesity and newly diagnosed type 2 diabetes, the 5:2 MR [meal replacement diet] approach achieved significant improvements in glycemic control and weight loss within a 16-week period, while also improving blood pressure and triglyceride and HDL-C levels,” said the researchers. “Therefore, 5:2 MR may potentially serve as an effective initial lifestyle intervention instead of antidiabetic drugs for early-stage type 2 diabetes.”
The study has some limitations. It only enrolled participants with an HbA1c of less than 9%, so the diet’s effectiveness in people with an HbA1c higher than that requires further research. Additionally, a longer period without antidiabetic medication might offer more insights into the effect of the previously stopped medication. Also, the long-term effectiveness of the 5:2 diet remains untested. Long-term follow-up studies are underway to assess the diet’s robustness.
The study was published in the journal JAMA Network Open.