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Despite benefits, intermittent fasting increases risk for hypoglycemia in type 2 diabetes

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February 23, 2018


Intermittent fasting increased hypoglycemia among patients with type 2 diabetes who were treated with hypoglycemic medications, according to the results of a study conducted in New Zealand.

However, fasting was also associated with improvements in weight, HbA1c and quality of life.

“With rising rates of obesity and [type 2 diabetes] worldwide, there is a need for accessible, safe and cost-effective treatments for both conditions,” Brain T. Corley, MBChB, of the Centre for Endocrine Diabetes and Obesity Research at Wellington Hospital, and colleagues wrote. “A very low-calorie diet can facilitate weight loss and improve glucose homeostasis; however, in those taking hypoglycemic medication, such calorie restriction increases the risk of hypoglycemia and the best way to avoid this remains unclear. One form of very low-calorie diet is intermittent fasting.”

Corley and colleagues performed an unmasked, randomized parallel group intervention trial of 41 adults with type 2 diabetes. All participants had BMI between 30 kg/m2 and 45 kg/m2 and were prescribed either metformin or hypoglycemic medications. The patients’ HbA1c ranged from 50 mmol/mol to 85 mmol/mol (6.7% to 10%).

The researchers randomly assigned patients to fast for either 2 consecutive (n = 19) or non-consecutive days (n = 22) each week for 12 weeks. Corley and colleagues reduced the dosage of medication on fasting days. The main outcome was the difference in hypoglycemia rates between the two arms, and secondary outcomes were quality of life, weight, glucose and HbA1c levels, liver function and change in diet.

Thirty-seven patients were included in the final analysis (n = 18, consecutive; n = 19 non-consecutive).

Fifty-three hypoglycemic events occurred among 15 patients over the course of 84 days of observation, Corley and colleagues wrote. More than half of patients (n = 22; 59%) did not experience a hypoglycemic event, which the researchers noted was less than they had expected. No patients reported severe hyperglycemic events.

During fasting, the risk for a hypoglycemic event doubled (relative rate, 2.05; 95% CI, 1.17-3.52), and the two groups had a mean hypoglycemia rate of 1.4 events during the intervention period, the researchers reported.

Despite reduced medication, fasting of any kind increased the hypoglycemia rate (relative rate, 2.05; 95% CI, 1.17-3.52).

The researchers reported that there was no difference between fasting on non-consecutive or consecutive days (relative rate, 1.54; 95% CI, 0.35-6.11). Both groups experienced improvements in HbA1c, fasting glucose, weight and quality of life.

“Although fasting days were associated with a twofold increase in the rate of hypoglycemia, it was not possible to determine if there was a significant difference in hypoglycemia between treatment arms given the low overall hypoglycemia rate,” Corley and colleagues wrote. “The intervention did result in weight loss, reduced HbA1c and a small improvement in the quality of life. Our study protocol could be adopted for the longer-term studies that will be required to assess the tolerability and sustained efficacy of an intermittent fast.” – by Andy Polhamus

Disclosures: The authors report no relevant financial disclosures.