‘I’m A Dietitian, And This Is When I Think Intermittent Fasting Actually Makes Sense For Someone’

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Intermittent fasting has been quite the buzzy eating phrase for the past few years now, and it’s understandable to have questions about it. After all, there are *a lot* of big claims about intermittent fasting, with some people swearing it does everything from improving heart health to helping you live longer.

But intermittent fasting doesn’t necessarily make sense for everyone—or even most people. Still, it may be worth a shot for some but, like many things, it’s a little complicated. That's why I'm here to break it down for you so you can safely gauge whether it's a practice that fits your lifestyle and health. Here are a few things to consider before giving intermittent fasting a try.

First, let’s go over what intermittent fasting means.

In case you’re not familiar with it or fuzzy on the details, intermittent fasting (sometimes referred to as “IF”) is an eating pattern where you have set periods of time designated for eating and fasting (or, when you don't eat).

There are a few different popular intermittent fasting schedules. The most popular is 16:8, where you have 16 hours of fasting followed by eight hours of eating. Another popular schedule is 12:12 (12 hours of fasting and 12 hours of eating). Some people will alternate fasting days, like in the 5:2 schedule, where you eat normally for five days and have two non-consecutive fasting days. In general, the 16:8 schedule seems to be the most manageable for people.

IF diets primarily get hyped in regards to weight loss—but hang on there.

There have been some studies on weight loss in intermittent fasting, but the data is a little murky. Most of the studies we have are on small sample sizes, looking at short periods of time. That makes it hard to say if one form of intermittent fasting is better for the other, or if any of these even “work.”

While limiting your eating window may be helpful in some ways, especially in people who tend to eat late at night, we still haven’t been able to tease out a weight-loss benefit when you compare it to a calorie restriction eating plan.

It’s really about the quantity *and* quality of the foods you eat—as opposed to the actual eating window, studies have shown. We still need more data on how much of an impact time restriction alone has on weight loss.

Fasting diets get swept up in controversy for other reasons too.

A lot of people—including plenty of nutritionists—slam intermittent fasting diets, and there are plenty of reasons why it’s controversial.

One of the most obvious ones is that it can be a very slippery slope for someone with a history of disordered eating or anyone who tends to become overly restrictive with food.

Another important piece is that we’re still learning a lot about intermittent fasting and gaining data on potential benefits. We don’t have a lot of data on pre-menopausal women and the impact of IF on hormones, for instance. Is intermittent fasting good or bad for these women? It's pretty difficult, even for a professional in the space like me, to give a hard-and-fast answer without enough data to back up claims in regards to specific groups of people.

As for the weight-loss claims, they’re just not really validated—and certainly not over the long term. It may simply be that some people lose weight in an intermittent fasting diet because they are restricting calories—not that the intermittent fasting diet itself does anything special.

Ultimately, IF diets really should be approached on a case-by-case basis with an individual and their health practitioner versus saying, “Everyone should try this.” It's easy to get caught up in big, sweeping claims, but remember that little is proven in regards to IF just yet.

For these reasons, intermittent fasting may not make sense for many people.

There are a few people that intermittent fasting just doesn’t make sense for. Those include someone training for an athletic event like a long distance race—you need to be consuming enough carbohydrates to support running a marathon, for example. Generally speaking, people who are training for an athletic event probably should not be doing intermittent fasting.

People with diabetes may not do well on an intermittent fasting diet as well and you definitely should not follow this eating plan if you’re pregnant or breastfeeding.

And, again, if you have a history of disordered eating, it’s best to take a pass on intermittent fasting. Trying one is too much of a slippery slope when they require you to implement strict rules on your eating.

But for others, intermittent fasting *can* fit into a healthy lifestyle.

Again, intermittent fasting isn’t for everyone and the data is a bit muddled in regards benefits. But I believe it has potential to be helpful for a few different groups.

That includes people who tend to eat late at night. Having set fasting windows can lessen the odds of overeating in the evening.

There is also some decent data around intermittent fasting and glycemic control, which is maintaining good blood sugar levels, particularly in people who are considered medically overweight or obese.

And what data in humans has pointed to so far is that intermittent fasting can reduce inflammation in the body. Inflammation is the root cause of so many health issues, including blood sugar issues like diabetes, high cholesterol, and high blood pressure. So if you deal with blood sugar, blood pressure, or cholesterol issues, speak to your doctor about IF.

Here’s my advice for how to decide if IF is right for you.

There are a lot of reasons why people decide to try intermittent fasting, and it’s really important to consider your personal goals. What are you hoping to accomplish by going on an intermittent fasting diet? Do you want more energy? To lose weight? Then, see if there is valid research to support your goal.

If you can, talk to a licensed health care provider who can give you some personalized guidance. It’s also important to factor in if you’re on any medications or have any underlying health conditions that might make intermittent fasting unsafe for you.

Finally, consider if this is even feasible for you. Not everyone is okay with having fasting windows. If you prefer to eat every three hours or so, this is definitely not the eating plan for you. But, if you want to find a way to stop late-night snacking and you like the idea of clear parameters, intermittent fasting may be a good fit.

Meet the expert: Jessica Cording, RD, is a nutritionist and author of The Little Book of Game Changers: 50 Healthy Habits for Managing Stress & Anxiety. She practices in New York City.

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