Last Updated on July 15, 2025 by Bertrand Clarke
In a groundbreaking study unveiled at the Endocrine Society’s annual meeting, ENDO 2025, in San Francisco, researchers from The First Affiliated Hospital of Zhengzhou University in China have illuminated a promising path for managing type 2 diabetes and obesity. Their findings suggest that a flexible dietary approach, specifically intermittent energy restriction (IER), could revolutionize how individuals control blood sugar and shed excess weight. Unlike rigid daily calorie counting, IER—commonly known as the 5:2 diet—offers a practical, sustainable way to achieve significant health improvements, making it a compelling option for the millions grappling with this chronic condition.
Type 2 diabetes, a condition affecting an estimated 537 million people globally as of 2021, is characterized by insulin resistance, where the body’s cells fail to respond effectively to insulin, leading to uncontrolled blood glucose levels. This metabolic disorder is closely tied to obesity, with up to 85% of cases linked to excess body weight, according to Diabetes UK. Left unmanaged, it can lead to severe complications such as heart disease, kidney failure, and vision loss. However, the new study highlights that strategic calorie restriction, particularly through IER, can yield measurable benefits in weight loss, blood sugar control, and even insulin sensitivity, offering hope for better disease management and, in some cases, remission.
The Study: A Fresh Look at Calorie Restriction
The research involved 90 participants with type 2 diabetes and obesity, with a mean age of 36.8 years and an average body mass index (BMI) of 31.7 kg/m². These individuals were randomly assigned to one of three dietary interventions for a 16-week, nutritionist-supervised program: intermittent energy restriction (IER), time-restricted eating (TRE), and continuous energy restriction (CER). Each group maintained the same weekly caloric intake, allowing researchers to compare the effectiveness of different approaches to calorie restriction.
- Intermittent Energy Restriction (IER): Participants consumed 500–600 kilocalories on two non-consecutive days per week while eating normally on the other five days, adhering to a weekly calorie goal.
- Time-Restricted Eating (TRE): Participants ate within a 10-hour window daily (e.g., 8 a.m. to 6 p.m.), fasting for the remaining 14 hours, with controlled food intake to match the weekly calorie target.
- Continuous Energy Restriction (CER): Participants followed a consistent low-calorie diet without specific time restrictions, maintaining a steady weekly calorie deficit.
Of the 90 participants, 63 completed the study, with results showing that all three approaches led to weight loss and improved blood glucose control. On average, participants lost 7.5 kilograms (16.5 pounds), and their glycated hemoglobin (HbA1c)—a key marker of long-term blood sugar control—dropped by over 1%, from a baseline of 7.42% to below the diabetic threshold of 6.5% in many cases. However, IER stood out as the most effective, particularly in reducing fasting blood glucose, improving insulin sensitivity, and lowering triglycerides, a type of fat in the blood linked to heart disease risk.
Dr. Zhang, a lead researcher, emphasized the flexibility of IER, noting, “The 5:2 diet allows normal eating for five days, which may be easier to sustain than daily restrictions or strict eating windows.” This adaptability contributed to an impressive 85% compliance rate among IER participants, significantly higher than the other groups. David M. Cutler, MD, a family medicine physician not involved in the study, told Medical News Today, “The fact that only 63 of 90 patients completed the study underscores the challenge of adhering to dietary restrictions, but IER’s higher compliance suggests it’s a more practical choice for many.”
Why IER Shines: The Science Behind the 5:2 Diet
The success of IER lies in its ability to trigger a metabolic switch from glucose to fat as the body’s primary energy source during fasting days. This process, known as ketosis, reduces insulin resistance and enhances metabolism, which can lead to improved blood sugar control and weight loss. Unlike continuous calorie restriction, which can slow metabolism over time, IER’s alternating pattern may prevent this adaptation, making it easier to sustain weight loss. Additionally, fasting days promote cellular stress responses that reduce inflammation and oxidative damage, further supporting metabolic health.
The study’s findings align with previous research on fasting diets. A 2021 study published in Diabetes Care found that a 5-day fasting-mimicking diet improved blood sugar control and reduced reliance on diabetes medications in type 2 diabetes patients. Similarly, a 2016 study in Diabetes Care demonstrated that an 8-week very low-calorie diet (VLCD) could normalize fasting plasma glucose within days by reducing liver fat and restoring hepatic insulin sensitivity. These results suggest that periodic calorie restriction, as seen in IER, may offer a powerful tool for managing type 2 diabetes.
A Practical Approach for Real-World Success
One of the most compelling aspects of IER is its practicality. Unlike TRE, which requires daily adherence to a specific eating window, or CER, which demands consistent calorie counting, IER allows individuals to maintain their usual eating habits for most of the week. This flexibility makes it easier to integrate into busy lifestyles, a critical factor given that adherence is a major barrier to long-term dietary success. As Dr. Zhang noted, “Patients should choose a form of energy restriction that fits their lifestyle, as adherence is key to sustained benefits.”
For those following IER, the two low-calorie days typically involve nutrient-dense, low-carbohydrate meals to stabilize blood sugar. For example, a 500–600 kcal day might include a breakfast of Greek yogurt with berries, a lunch of grilled chicken and leafy greens, and a dinner of vegetable soup. These choices align with recommendations from the National Institute of Diabetes and Digestive and Kidney Diseases, which emphasizes vegetables, lean proteins, and healthy fats for diabetes management.
Challenges and Considerations
Despite its promise, IER is not without challenges. The study noted a 30% dropout rate, highlighting the difficulty of adhering to any restrictive diet, even one as flexible as IER. Participants reported mild hunger and fatigue on fasting days, though these symptoms often subsided as their bodies adapted. Additionally, individuals on diabetes medications, such as insulin or SGLT-2 inhibitors, may need to adjust dosages on fasting days to avoid hypoglycemia, a risk underscored in a 2025 Medical News Today article on intermittent fasting. Consulting a healthcare provider is essential to ensure safety.
Moreover, the study’s relatively small sample size and short duration (16 weeks) call for further research to confirm long-term benefits and generalizability across diverse populations. Dr. Zhang advocated for future studies to include broader age groups, ethnicities, and diabetes durations to better understand IER’s efficacy.
Broader Implications for Public Health
The rising prevalence of type 2 diabetes—projected to affect nearly 10% of the global population by 2050—underscores the urgency of accessible, effective interventions. IER’s high compliance rate and significant health benefits position it as a scalable solution for public health systems strained by the diabetes epidemic. In the United States alone, where 37.3 million people had diabetes in 2019, adopting flexible dietary strategies could reduce healthcare costs associated with complications like cardiovascular disease and kidney failure.
Beyond weight loss and blood sugar control, IER may offer additional benefits. A 2023 study in Diabetologia found that a low-energy diet led to sustained reductions in blood pressure, with 28% of participants discontinuing antihypertensive medications for at least two years. These findings suggest that IER could address multiple facets of metabolic syndrome, a cluster of conditions including high blood pressure, high cholesterol, and obesity that heightens diabetes risk.
Looking Ahead: A New Era in Diabetes Care
The Zhengzhou University study marks a pivotal moment in diabetes management, highlighting the potential of IER to empower individuals with type 2 diabetes to take control of their health. By offering a flexible, sustainable alternative to traditional calorie restriction, the 5:2 diet could redefine how we approach this chronic condition. As researchers call for larger, longer-term studies, the message is clear: small, strategic changes in eating patterns can yield big results.
For individuals with type 2 diabetes, the path to better health may start with just two low-calorie days a week. With guidance from healthcare professionals and a commitment to sustainable habits, this approach could not only manage symptoms but also pave the way for lasting remission, offering a brighter, healthier future.
