Intermittent energy restriction stands out for improving outcomes in people with T2D, obesity

In individuals with type 2 diabetes (T2D) and obesity, an intermittent energy restriction (IER) diet helps with glucose control, with the advantage of improving insulin sensitivity, reducing triglycerides, and being easier to follow compared with other dietary interventions, as shown in a single-centre randomized controlled trial.

After a 16-week intervention, the primary endpoint of glycated haemoglobin (HbA1c) levels decreased for participants allocated to the IER, time-restricted eating (TRE), and continuous energy restriction (CER) groups. But the absolute change was more pronounced in the IER group (–1.56 percent vs –1.44 percent vs –1.03 percent, respectively; p=0.23). [ENDO 2025, abstract OR19-08]

Similarly, the IER group showed the largest reduction in body weight, although the difference from those seen in the TRE and CER groups were not significant (–8.6 vs –8.2 vs –5.7 kg; p=0.39).

Results for other secondary outcomes favoured IER. Compared with TRE and CER, IER resulted in a significant increase in insulin sensitivity (Matsuda index, 80.23; p<0.05) as well as marked reductions in fasting blood glucose (–2.3 mmol/L; p<0.05) and triglycerides (–1.139 mmol/L; p<0.05).

The IER group also had the highest patient adherence at 85 percent, followed by the CER group at 84 percent, and the TRE group at 78 percent (IER and CER vs TRE: p<0.05).

Changes in uric acid and liver enzymes did not significantly differ across the three groups. Hypoglycaemia occurred in two patients each in the IER and TRE group and in three in the CER group.

“This study is the first to compare the effects of three different dietary interventions—IER, TRE, and CER—in managing T2D with obesity,” said lead study author Dr Haohao Zhang from the First Affiliated Hospital of Zhengzhou University in Zhengzhou, China.

Zhang emphasized that their work fills an evidence gap, providing scientific evidence that can aid clinicians treating patients with T2D and obesity when choosing appropriate dietary strategies.

How intermittent fasting works

Intermittent fasting regimens, including IER and TRE, have attracted considerable attention as an alternative to the traditional CER for weight management and metabolic improvement. The idea is to consume very few calories on certain days, such as in IER, or to restrict food intake to a specific window of time, such as in TRE. This temporary restriction of calories triggers the metabolic adaptive mechanisms, inducing the body to use stored fat as a source of energy, potentially leading to weight loss and improved metabolic health. [Diabetes Obes Metab 2025;27:920-932; J Obes Metab Syndr 2022;31:230-244]

In the study, participants in the TRE group had to restrict daily eating into a fixed 10-h window. They could choose to eat between 8 am and 6 pm, for example, and fast for the remaining 14 h.

Meanwhile, the IER group followed a 5:2 or twice-weekly fasting regimen. Participants were required to control calorie intake on any 2 chosen days of the week, while maintaining a normal diet without deliberately restricting food types on the remaining 5 days. The high adherence observed in the IER group could be attributed to the greater flexibility regarding fasting duration, allowing for normal eating most of the time. [Int J Endocrinol 2025;2025:6658512]

For the study, Zhang and colleagues enrolled 90 participants with T2D and obesity. These participants were randomly assigned to undergo IER, TRE, or CER for 16 weeks, with a similar weekly intake of calories across all groups. A nutritionist supervised and guided the dietary regimens throughout the intervention period.

A total of 63 participants completed the 16-week intervention. Their average age was 36.8 years, and 45 were male. The average disease duration was 1.5 years, and the baseline BMI and HbA1c values were 31.7 kg/m² and 7.42 percent, respectively.