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HbA1c improves just as much on dieting only two days a week

Cutting calories two days a week improves glycaemic control over a year as well as constant dieting

Louise Prime

Monday, 23 July 2018

Twice-weekly calorie restriction is at least as effective as conventional calorie restriction in improving glycaemic control in people with type 2 diabetes, according to new research. The authors of the study*, published this weekend on JAMA Network Open, found comparable changes in haemoglobin A1c (HbA1c) over a year, in the two groups.

Researchers led from the University of South Australia in Adelaide pointed out that people can find it hard to adhere to conventional calorie-restriction diets over time, and that there is already evidence that intermittent calorie restriction can be effective in weight loss. So they conducted a noninferiority trial to compare the long-term effects on HbA1c of intermittent calorie restriction – for two days a week – with the effects of continuous calorie restriction.

They randomised 137 men and women with type 2 diabetes to one of two diets, for 12 months. They assigned 70 patients to a diet of intermittent calorie restriction (500-600 calories/day) on two non-consecutive days each week, and eating their usual diet on the other five days; and the other 67 patients to a daily calorie restriction diet (1,200-1,500 calories/day), between April 2015 and September 2017. At baseline, mean HbA1c was 7.3% and mean body mass index was 36.0.

The intention-to-treat analysis showed that among the total 97 people who completed the trial, average change in HbA1c over 12 months was comparable between the continuous and intermittent calorie restriction diet groups, falling by 0.5% and 0.3% respectively.

Mean weight change was also similar between the continuous and intermittent energy restriction groups ( 5.0kg vs 6.8kg), but the between-group difference did not meet the pre-set criteria for equivalence.

The researchers acknowledged certain limitations of their study, such as that participants already had relatively well controlled type 2 diabetes; medication adjustments can complicate interpreting changes in HbA1c levels; and study participants had more contact with a dietitian than is usual in a clinical setting.

Nevertheless, they concluded: “Intermittent energy restriction is an effective alternative diet strategy for the reduction of HbA1c level comparable to continuous energy restriction in patients with type 2 diabetes, and it may be superior to continuous energy restriction for weight reduction. Intermittent energy restriction is acceptable for most patients with type 2 diabetes, and safety can be ensured for patients who are not using glycaemic agents likely to cause hypoglycaemia.”


*Carter S, Clifton PM, Keogh JB. Effect of intermittent compared with continuous energy restricted diet on glycemic control in patients with type 2 diabetes: a randomized noninferiority trial. JAMA Network Open 2018; 1(3): e180756. doi:10.1001/jamanetworkopen.2018.0756

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