Weight loss improves glycaemic control in type 2 diabetes mellitus (T2DM). However, as achieving and maintaining weight loss is difficult, alternative strategies are needed. Our primary aim was to investigate the effects of intermittent energy restriction (IER) compared to continuous energy restriction (CER) on glycated haemoglobin A1c (HbA1c). Secondary aims were to assess effects on weight loss, body composition, medication changes and subjective measures of appetite. Using a 2-day IER method, we expected equal improvements to HbA1c and weight in both groups.

Sixty-three overweight or obese participants (BMI 35.2 ± 5 kg/m²) with T2DM (HbA1c 7.4 ± 1.3%) (57 mmol/mol) were randomised to a 2-day severe energy restriction (1670-2500 kJ/day) with 5 days of habitual eating, compared to a moderate CER diet (5000-6500 kJ/day) for 12 weeks.

At 12 weeks HbA1c (−0.7 ± 0.9% P < 0.001) and percent body weight reduction (−5.9 ± 4% P < 0.001) was similar in both groups with no group by time interaction. Similar reductions were also seen for medication dosages, all measures of body composition and subjective reports of appetite.

In this pilot trial, 2 days of IER compared with CER resulted in similar improvements in glycaemic control and weight reduction offering a suitable alternative treatment strategy.