It's the trendy diet method, but does intermittent fasting really work?

Diet trends come and go, but intermittent fasting, a form of dieting based around periods of non-eating followed by periods of concentrated eating, has somehow endured.

In 2020, it became the most popular form of dieting in the U.S., according to the Food Information Council's Food and Health Survey, and it remains a significant part of diet culture. Proponents claim it can help with everything from weight loss to cholesterol and blood sugar management, despite some less than promising research.

So does intermittent fasting really work? It's a complicated question with an equally complicated answer, says Rachel Rodgers, an associate professor of applied psychology at Northeastern University.

Rodgers, who specializes in body image, disordered eating and health-related behaviors, spoke to Northeastern Global News about her skepticism around intermittent fasting, the issues with diets more generally and why modern food production has made eating in moderation nearly impossible. Her comments have been edited for brevity and clarity.

What is intermittent fasting?

That is an important question because what people call intermittent fasting can look quite different. There is intermittent fasting that is alternating days on which people eat ad libitum, those being called "feast days," and those where their intake is much reduced, "fast days." It can look like time restricted fasting where people will not eat for a certain amount of consecutive hours and then eat the rest of the time. It can be periodic fasting, whereby you might fast for up to 24 hours twice a week but not on alternating days. So, it really depends.

What is the professed benefit of intermittent fasting?

I'm not convinced about the benefits. In terms of the clinical literature, we really don't know that much. There are three or four clinical trials that have been conducted on these behaviors, only one of which was a really rigorous one with follow-ups where people were assessed multiple times after the end. The rest of the literature is piecemeal in terms of what the studies actually look like, what they were actually assessing.

There is evidence that different forms of intermittent fasting are associated with some decreases in weight. However, that should be placed in the context that up to 40% or 50% of the people drop out of the clinical trials [and] that it's not clear that they're actually adhering to the protocol. Any changes that we're seeing are not clearly attributable to what the intervention was actually designed to do and to measure. All that aside, there do seem to be some small reductions in weight in people who are engaging in these kinds of behaviors.

In terms of the mechanisms at work, we don't really know. Is it just that people are eating less? Is it that there are metabolic benefits? It's possible. It's a little bit unclear. The other purported health benefits are really unclear in terms of the data. Anything about health indicators is not clear at all.

Is intermittent fasting an effective, helpful form of dieting or health-related behavior?

I am personally wary of any behavior that is specifically designed to target weight rather than to help people develop a comfortable and attuned relationship to their eating behaviors in a way that is going to work for them sustainably. I'm also wary of anything that has a rule because once you get into a rules system, rules get broken and then you get into black and white thinking. You've broken the rule––everything's gone wrong. As we know, that's the basis of a binge-restriction cycle. Intermittent fasting is essentially a form of dieting, and that's something I generally find less helpful as a philosophy.

Are there any long-term effects that people need to look out for?

The problem is we don't have the data to predict that. My main concern is that it might increase peoples' reliance on rule-based patterns and, potentially, disordered eating. It could increase other mental health concerns if it becomes hard to sustain or people feel like they're failing at something. But we don't really know.

Why do you think intermittent fasting has become so popular?

At any point in time you're going to have a certain kind of dieting that becomes fashionable.

One of the marketing strengths of this particular one is that it's not so much about what you can eat but when. Sometimes that can be easier for people because we all have particular foods that we like to eat, so not being told that you can't have something, just that it's about when, can be perceived as easier.

Also, one of the things that's difficult in our society, due to an intense amount of food marketing as well as the way foods are engineered, is eating in moderation. This is not the fault of people. It's a logical result of the food environment we live in, and therefore having that 'now I can eat, now I just don't eat' [approach] avoids the difficulties in moderation.

If, as you say, intermittent fasting and other diets are not a helpful way to approach eating, what strategies or approaches do you think are more helpful?

There are other approaches to eating that I think are more helpful. These are ones that are flexible and that are based on the idea that eating will look different for every person and it might look different for each person at a different point in time. These ways of eating are much more in tune with physical cues, or hunger and satiety and being able to recognize those bodily signals. Am I hungry? Am I not hungry? What would I like to eat now? Why am I thinking I would like to eat that thing now? Am I just bored? Am I not?

There is a pattern of eating that is called intuitive eating that's really based on rejecting diet culture and being attuned to those things. Mindful eating is another approach that really focuses on enjoying the foods and paying attention in a nonjudgmental way that also gets into the idea that eating is a process rather than, "What's this going to do for me? Is it going to make me immortal? Am I going to be beautiful and shiny?"

I think the question we should be asking ourselves when it comes to intermittent fasting is, how did we come to live in a world where we need to be not eating half of the time? Because if this works, if this is the way forward, it seems kind of drastic. How did we get to a place where our food environment is so pressurizing and the foods that we're surrounded with are so dense and so difficult to eat in moderation that this is now seeming like a perfectly realistic option?

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