Intermittent fasting, periodic fasting, and type 2 diabetes: What does the research say?

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Intermittent energy restriction (IER) and periodic fasting (PF) are two types of diets that involve eating fewer calories or none at all for certain periods.

Some people believe that these diets can help manage type 2 diabetes (T2D), a health condition that affects how your body uses sugar.

However, this idea is still up for debate. This review looks at what the latest studies say about it.

Data Sources

We looked at several databases to find studies for this review. These included popular medical and academic databases like PubMed, Embase, and the Cochrane Library, among others.

Our last search was on November 11, 2022. We focused on studies that looked at how IER or PF diets affect adults with type 2 diabetes.

What Did We Find?

Our search found 692 unique studies. After a close look, we included 13 original studies in our review. These studies varied a lot in their methods, diets, and length.

So, we couldn’t combine their results into one big analysis. Instead, we summarized the results from each study.

Effects on Blood Sugar and Medication Use

One of the ways doctors check how well someone’s diabetes is controlled is by measuring a substance in the blood called glycated hemoglobin (HbA1c).

This substance can tell us the average blood sugar level over the past 2-3 months. Out of the 10 studies that looked at this, 5 found that IER or PF diets lowered HbA1c levels.

Another way to check blood sugar control is by measuring fasting glucose, which is the blood sugar level after not eating overnight.

Out of the 7 studies that looked at this, 5 found that IER or PF diets lowered fasting glucose levels.

Some studies also looked at whether these diets could reduce the need for glucose-lowering medication. Four studies found that people could take less medication during IER or PF.

Long-Term Effects

Two studies looked at what happened one year or more after the diet ended. Unfortunately, the benefits to HbA1c or fasting glucose usually did not last in the long term.

Quality of Studies

We also checked how reliable the studies were. Most studies had at least some risk of bias, which means that their results might not be completely trustworthy.


Based on our review, IER and PF diets can improve blood sugar control in people with type 2 diabetes, at least in the short term.

These diets might also let people reduce their glucose-lowering medication.

However, we need more high-quality studies to confirm these findings and to see whether the benefits can last in the long term. It’s also crucial to remember that everyone is different.

What works for one person might not work for another. Always talk to a healthcare provider before starting a new diet or changing your medication.

The research was published in Nutrition Reviews.

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