Here's why one RD says you should proceed with caution despite the purported benefits of this diet trend.

By Jessica Cording, MS, RD, CDN
Updated August 28, 2019
Photo: mactrunk/Getty Images

Any dietitian or nutritionist will likely admit that they have a list of the questions most commonly asked by clients. Typically, that list evolves based on the latest diet and wellness trends—a couple of years ago, everyone wanted to talk about the paleo diet, and while the Whole30 craze is still alive and well, I get a lot more questions now about the keto diet. Another big one right now: intermittent fasting.

What is intermittent fasting?

More of an "eating pattern" than an actual diet, intermittent fasting (IF) is characterized by cycling between periods of eating and fasting. There are several approaches, but the most popular are those that involve either daily 16-hour fasts in which you eat all your food in an eight-hour window, or an IF pattern in which someone fasts for 24 hours, usually twice per week. There's also the 5:2 plan, where you eat "normally" for five days and then for the other two days, consume only about 500 to 600 calories. While there are exceptions, in general, IF patterns tell you when to eat, but not necessarily what to eat.

What are the intermittent fasting benefits?

Now's probably the time to be up-front: I am not a fan of intermittent fasting.

While research has shown some potential health benefits of intermittent fasting, as a dietitian and health coach who focuses on sustainable lifestyle approaches to wellness, I can't quite get on board with recommending that someone just not eat. Fasting can be a slippery slope to unhealthy habits and a screwy relationship with food.

That doesn't mean I won't work with someone who wants to explore IF-it just means we need to discuss why you're interested in using this method to reach your goals and whether there might be other options to achieve the health benefits you're after in a more sustainable way.

Weight management is probably the number-one reason people ask me about intermittent fasting. While studies have shown that intermittent fasting benefits may include weight loss and improved metabolism, this eating pattern has also been researched for its impact on insulin resistance, as well as for its potential to decrease inflammation, enhance cell repair, and support a healthy gastrointestinal tract. Sounds great, right? Not so fast.

Here are the health concerns about intermittent fasting.

The main issue that comes up is sustainability—meaning, can you maintain this way of eating, and, more so, should you? Many people find they feel great while following an intermittent fasting plan but struggle when they try to stick with it for a prolonged period. Figuring out how to fit those fasting and eating periods into your work and social life, and fuel and refuel appropriately around your workouts, can be a logistical nightmare and also a health challenge. This is especially true if you work long days, wake up really early, or go to bed very late. It can also be tricky for people who lack a sense of routine in their day-to-day life. While some people have found it motivates them to get into a more consistent schedule, many have gotten frustrated for not being able to keep it up. When your self-esteem takes a hit like that, it can trickle into other areas of your life. (Must read: Why You Should Give Up Restrictive Dieting Once and for All)

I've seen many people who hop on and off the IF bandwagon start to feel out of touch with their hunger and fullness cues. This mind-body disconnect can make it difficult to establish an overall healthy diet for the long haul. For certain people, this could lead to or resurface disordered eating behaviors. (BTW, have you heard of orthorexia? It's the eating disorder masking itself as a healthy diet.)

If you still want to try intermittent fasting...

With all that said, if you've consulted your doctor and/or your certified nutritionist, and you're intrigued by the potential benefits of intermittent fasting, here are a few tips to keep in mind.

Identify what intermittent fasting benefits you're after.

Are you hoping to lose weight with intermittent fasting? Is there another health reason? Have you tried other approaches to meeting your goal? If yes, why didn't they work? Zeroing in on what intermittent fasting health effects you hope to accomplish and the motivations behind them will help you prioritize foods and strategies that help you get there in a healthy way.

Consider your approach.

Decide whether a daily 16/8 approach or something more like a weekly 5:2 plan will work better for your stomach and schedule. When do you usually get hungry throughout the day? What time do you wake up and go to bed? How often and what time of the day do you work out? All of this will help determine when you are in fasting mode. For example, if you routinely hit the sack after midnight, closing the kitchen at 6 p.m. probably won't be so easy.

Make intermittent fasting work around you.

Take into account when you tend to go to sleep and wake up. Then factor in when you like to exercise. What is your work schedule like? How about your social life? This will help you figure out how to spread out your fasting and eating phases, so you're never starving, cranky, and struggling to maintain your energy and focus.

Have an exit strategy.

Are you thinking of IF as a long-term plan? While I don't recommend it as such, if you intend to be intermittently fasting forever (whew), you better make sure you have a plan to help reintroduce a more regular eating schedule back into your life. I see a lot of people trip up when they try to come off an IF cycle because they can't seem to get reacquainted with their appetite and hunger cues. If you're serious about doing IF in a healthy, mindful way, come up with a post-IF plan (perhaps together with a dietitian) so you have something to guide you.