Intermittent fasting for insulin-treated patients with type 2 diabetes?

Intermittent fasting — and one of its variants, "time-restricted eating" — are increasingly popular approaches to weight management. But are these methods feasible and safe for people with diabetes, especially those who take insulin? To address this question, Austrian researchers conducted a study that involved 46 carefully selected insulin-treated patients with longstanding type 2 diabetes; at baseline, mean glycosylated hemoglobin (HbA1c) was 8.3%, mean weight was 100 kg, and mean daily insulin dose was 56 units.

Patients were randomised to either 3 nonconsecutive days of intermittent fasting weekly or to usual care. In the intervention group, patients ingested only 25% of their recommended caloric intake on fasting days; that intake was limited to a single meal (either breakfast or lunch). Compared with the control group at 12 weeks, the intermittent fasting group had significantly greater weight reduction (mean, 5 kg), HbA1c reduction (mean, 0.7%), and insulin-dose reduction (mean, 11 units). Notably, patients in the fasting group were given detailed insulin adjustment protocols for fasting days, and no severe hypoglycemia occurred.

This study suggests that intermittent fasting is feasible in selected insulin-treated patients with type 2 diabetes — provided that the patient is capable of following protocols to adjust insulin doses carefully on days when calories are restricted. But we still need longer-term data to assess safety over many months or years and to determine whether improvement in glycemic control and weight is sustained.