Did Recent Research Show “No Benefit” To Intermittent Fasting?
A flurry of recent headlines gained widespread attention claiming that a study on intermittent fasting and time-restricted feeding found “no benefit”. Unfortunately, these headlines, while reporting on real research, are entirely misleading about the conclusion. So what did the study really say, and what is the right conclusion? In this post, we’ll dig into those headlines and the source research to figure out what it really means about the benefits of intermittent fasting.
The headlines in question were all reporting on a recent study on intermittent fasting. The headline that grabs the most attention, both for what it says, and for the source, is this one, from the New York Times: “Scientists Find No Benefit to Time-Restricted Eating“. While the Times is the most prominent source to report this conclusion, there were many others as well.
That certainly sounds like damning evidence against intermittent fasting, but it doesn’t tell the full story. If we dig into the article itself, the Times is reporting on a research study comparing time restricted feeding to traditional calorie counting diets in obese individuals. Early in the article, the author quotes a researcher as saying “There is no benefit to eating in a narrow window”. However, a paragraph later, we find the following:
“Both groups lost weight — an average of about 14 to 18 pounds — but there was no significant difference in the amounts of weight lost with either diet strategy“.
So this complicates the interpretation a bit: we’ve gone from “no benefit”, to “intermittent fasting helped people lose weight, but the weight loss was not meaningfully different than the traditional calorie counting methods”. The goalposts have moved!
So while the Times headline is incomplete but technically not wrong, many articles reporting on what was written in the Times that are flat out wrong: “Study Shows Time-Limited Eating Doesn’t Fight Obesity“. To be fair, some news organizations did a slightly better job by mentioning what it was being compared to. For example, this headline from CNN: “Time-restricted eating no better than counting calories, study finds“. This headline implies, correctly, that there are benefits of intermittent fasting, but also that those benefits are “no better than counting calories”. That’s a claim we take issue with below, but at least it’s closer to the true picture.
So let’s forget the headlines for a moment. What does the source research material actually say about the benefits of intermittent fasting? The research article in question is a paper titled “Calorie Restriction with or without Time-Restricted Eating in Weight Loss” published in the New England Journal of Medicine. The researchers compared a traditional calorie restricted diet to a calorie restricted diet with intermittent fasting in obese individuals. They found that both groups lost weight and both groups saw improvements in other health metrics, but there were no significant differences between the two.
Their conclusion, “Among patients with obesity, a regimen of time-restricted eating was not more beneficial with regard to reduction in body weight, body fat, or metabolic risk factors than daily calorie restriction“. In other words, intermittent fasting is an effective way to lose weight and improve other health metrics. It’s just not necessarily any better than calorie counting on the specific things they measured.
So the source research itself concludes that IF can help people lose weight and improve a variety of health metrics. So why are there so many article reporting what seems to be the opposite conclusion from this research? In order to understand how they got from point A to point B, we need to parse the exact wording a bit more carefully.
What Do The Headlines Mean by “No Benefit”?
When we see a phrase like “no benefit” in these headlines, there are two important questions we need to ask:
- No benefit relative to what?
- No benefit on which metric?
To answer the first question, “no benefit relative to what?”, we find that there is no benefit relative to another effective means of losing weight. In other words, intermittent fasting is effective, but not more effective than calorie counting on these specific metrics.
Now that we’ve established that intermittent fasting is in fact effective, contrary to what the headline might imply, we can look at the second question, “no benefit on which metric?”. This study is looking at the weight loss as the primary measurement. But total weight loss is not the only metric we’re interested in with intermittent fasting–there are many other health benefits that it may bring, some of which, but not all are measured in this research. We detail some of the other benefits on the frequently asked questions page, with links to the research.
In fact, there’s one major practical benefit that many people experience when they try IF: adherence. Even if we were to find that IF is no better than calorie restriction for weight loss and other health metrics, but it is easier for people to adhere to, that would be a huge benefit for intermittent fasting. And while research on the topic is ongoing, current research suggests this to be the case: “TRF may be an easily understandable and readily adoptable lifestyle change with the potential to reduce abdominal obesity and lower the risk for cardiometabolic diseases”.
Taken together, the answers to these questions paint a very different picture than the headlines suggest: intermittent fasting is effective for losing weight and for a variety of other health metrics. Calorie restriction is also effective for weight loss and the same health metrics, though there are many other suspected benefits of IF that are not considered in the research.
Conclusion–on the Benefits of Intermittent Fasting
Scientific studies like the one discussed here look at very specific outcomes in extremely specific circumstances, and as such, it’s generally not a great idea to extrapolate broad conclusions from a research study like this. Sadly, it’s extremely common in scientific reporting to do so, and the misinterpreted headlines are then reported and extrapolated further until it’s unrecognizable from the original research.
The claim of “no benefit” in time restricted feeding is not “literally” wrong, but it’s incomplete and thus wildly misleading as it does not explain which metric is being compared or relative to what outcome as a control. So my alternative headline, based on the same research is: “Time restrictive feeding an effective way to lose weight and improve a variety of related health metrics such as blood pressure and insulin resistance”. The research actually helps confirm the benefits of intermittent fasting.
And just in case you think my interpretation is biased by the fact that I’m a fan and follower of intermittent fasting, here’s a response from other researchers that not only echos the concerns around the interpretation of the results, but also about the methods of the research itself.