Big Claims, Vexing Flaws of an Intermittent Fasting Study

Clinical research is hard to do right – especially if the goal is to discover the true answer to a scientific question. Because scientists are human, they bring passion to their work. But they have to set aside those passions in designing and conducting research so that their research will hold up to scrutiny. Along the way, many questions arise. Compromises and limitations are inevitable. But sometimes, enthusiasm takes over. So when we saw big claims for a small study of intermittent fasting to cause remission in type 2 diabetes, we had questions about some vexing flaws.

In the Journal of Clinical Endocrinology and Metabolism, Xiao Yang and colleagues claim that intermittent fasting brings a sustained remission to nearly half of a small group of patients randomly assigned to it. The researchers conclude boldly:

“It could be a paradigm shift in the management goals in diabetes care.”

In a tweet, Eric Topol sums it up nicely: “Yes, too good to be true … Worth further study.”

An RCT of 72 Patients

On the surface, the design of the study makes it credible. It’s a small RCT with 36 patients assigned to the intermittent fasting group and the same number assigned to a control group. This was a three-month intervention with follow-up for three months to assess initial rates of diabetes remission. Further follow-up came at 12 months to assess the durability of that remission. The definition of remission was an HbA1c less than 6.5 percent at least three months after discontinuing diabetes medications.

The initial rate of remission was 47 percent in the treatment group and 2.8 percent in the control group. The treatment group lost about nine percent of their starting body weight while the control group barely had any change at all.

One obvious issue is the small size of the study. Just because these researchers could find 36 people who responded well to intermittent fasting, we cannot conclude that this approach will be broadly effective in the population of people with type 2 diabetes. In fact, to recruit the 72 patients in this study, the researchers had to screen 246 patients. Even after 117 of them met screening criteria for the study, another 45 patients fell out of the study. If an investigator judged that the a subject might be “unsuitable” for any reason, the study excluded them.

Registered Only After the Fact

But the biggest problem for this RCT was the lack of a prospective study registration. Researchers began recruiting patients in January of 2019. Some of the patients finished their treatment as early as May of that year. But the study protocol wasn’t registered until September of 2020.

This is a breach of publication ethics because clinical trial protocols must be registered before recruiting the first patient. JCEM says the journal will not consider any study for publication if it doesn’t meet this requirement.

In short, this study of Intermittent fasting makes some big claims, but it has vexing flaws that should have disqualified its publication.

Intermittent Fasting: Potentially Helpful for Some

Absence of proof is not proof of absence. Certainly, there’s plenty of reason to believe that intermittent fasting can be helpful to some people with type 2 diabetes. But can it help many people achieve remissions in type 2 diabetes? We will remain skeptical until robust evidence supports such a conclusion.

Click here for the Yang study and here for a recent narrative review.

The House with Cracked Walls, painting by Paul Cezanne / WikiArt

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December x, 2022