Intermittent fasting appears effective for HbA1c reduction in type 2 diabetes

Patients on the intermittent energy restriction diet ate 500 to 600 kcal/d on two nonconsecutive days each week and followed their usual diet on the other days. They were compared to a group eating 1,200 to 1,500 kcal/d.


Intermittent energy restriction appears to reduce HbA1c level in patients with type 2 diabetes and is an acceptable alternative to continuous energy restriction, according to a small recent study.

Researchers in Australia compared intermittent energy restriction with continuous energy restriction over a 12-month period in overweight or obese adult patients with type 2 diabetes and examined the effects on glycemic control and weight loss. One hundred thirty-seven patients (56% women; mean age, 61 years) were randomly assigned to intermittent or continuous energy restriction between April 7, 2015, and Sept. 7, 2017. Those on the intermittent energy restriction diet ate 500 to 600 kcal/d on two nonconsecutive days each week and followed their usual diet on the other five days, while those on the continuous energy restriction diet ate 1,200 to 1,500 kcal/d every day each week. Both diets were followed for 12 months.

Patients in both groups met with a dietitian every two weeks for the first three months of the study and every two to three months for the final nine months of the study. A medication management protocol was also followed for all patients. The study's primary outcome measure was change in HbA1c, and the secondary outcome was weight loss. Equivalence was set at a 90% CI margin of ±0.5% for change in HbA1c and at ±2.5 kg for weight loss, with ±1.75 kg for loss of fat mass and ±0.75 kg for loss of fat-free mass. The study results were published July 20 by JAMA Network Open.

Seventy patients were assigned to the intermittent energy restriction diet, and 67 were assigned to the continuous energy restriction diet. At baseline, mean body mass index was 36 kg/m2 and mean HbA1c level was 7.3%. Ninety-seven patients completed the trial, with dropout rates of 31.3% in the continuous energy restriction group and 27.1% in the intermittent energy restriction group. In intention-to-treat analysis, reductions in mean HbA1c level during the study were similar: −0.5% in the continuous energy restriction group versus −0.3% in the intermittent energy restriction group (P=0.65), with a between-group difference of 0.2% (90% CI, −0.2% to 0.5%), meeting the criterion for equivalence.

Mean weight change was also similar for both energy restriction groups (−5.0 kg for the continuous energy restriction group vs. −6.8 kg for the intermittent group; P=0.25). However, the between-group difference did not meet the criterion for equivalence for mean weight change (−1.8 kg; 90% CI, −3.7 to 0.07 kg), fat mass (−1.3 kg; 90% CI, −2.8 to 0.2 kg), or fat-free mass (−0.5 kg; 90% CI, −1.4 to 0.4 kg). Occurrence of hypoglycemic and hyperglycemic events in the first two weeks of treatment were similar in both groups (mean, 3.2 events in the continuous energy restriction group and 4.9 events in the intermittent energy restriction group; P=0.28). More than one-third of the hypoglycemic and hyperglycemic events (35%) occurred in patients taking sulfonylureas, insulin, or both.

The authors noted that the patients in their study had well-controlled type 2 diabetes, decreasing generalizability, and that blood glucose monitoring was done only with fingerprick testing, among other limitations. Based on their results, they concluded that intermittent energy restriction can be an effective alternative diet for reducing HbA1c in patients with type 2 diabetes and may outperform continuous energy restriction for weight reduction, although a larger trial would be needed to confirm the latter observation. They noted that intermittent energy restriction is an option for most patients with type 2 diabetes and is safe for those not taking medications with high risk for hypoglycemia. Regular monitoring is essential for patients taking sulfonylureas, insulin, or both, the study authors wrote.