How Intermittent Fasting Impacts Your Sleep (Hint: It’s Not Great)

Intermittent fasting has been a hot topic in the nutrition and wellness industry. In the past year, headlines have read, “8-hour time-restricted eating linked to a 91 percent higher risk of cardiovascular death,” (1) “Intermittent fasting probably won’t harm your heart if you do it right,” (2) and “Research shows that intermittent fasting is safe and effective.” (3)

Is your head spinning yet?

Health experts, celebrities, and wellness gurus have a plethora of conflicting opinions on intermittent fasting (IF), which involves restricting your food intake for a certain number of hours per day (often 16 hours) or restricting food intake on certain days of the week. (4) To make matters even more confusing, current research seems to take the same convoluted stance on the health trend. 

Supporters of the intermittent fasting trend might say that it improves memory, promotes fat loss, reduces inflammation, and is beneficial for heart health. That said, it may cause some people to experience unpleasant side effects, including headaches, insomnia, dizziness, and nausea. (4) 

What Do Experts Say About IF and Sleep? 

When it comes to sleep, the answer is also a little bit fuzzy. Jabe Brown, founder of Melbourne Functional Medicine, told Sleepopolis, “The dance between intermittent fasting and sleep is intricate, with some research suggesting a promising, albeit complex, relationship.” (5) 

Registered dietician and nutrition writer Catherine Gervacio seems to agree. “Intermittent fasting can both impact sleep, negatively and positively. It varies from one person to another.” (6) 

There are so many variables at play in the relationship between IF and sleep, making it difficult to pinpoint one concrete answer. There are several types of intermittent fasting regimens, and each individual may respond differently.

Gervacio told us about the potential positive side of the trend, saying that when done properly, practicing intermittent fasting can actually improve sleep because of its potential to aid in blood sugar regulation and hormone balance. 

Brown explained its potential positive impact on sleep in detail, saying some studies suggest that fasting increases the production of orexin-A, which is associated with wakefulness. He says that according to the research, people who practice intermittent fasting may have lower levels of the wakefulness hormone orexin-A at night and higher levels during the day. (6)  

So how can this help to improve sleep?

“This aligns with our observations that adhering to eating patterns which complement natural biological cycles can indeed foster a more restorative sleep experience,” says Brown. 

IF and Negative Sleep Impacts

With the above positives in mind, it’s important to note that these IF benefits for sleep might not be universally experienced.

“Some may experience disrupted sleep patterns or difficulty falling asleep especially if they aren’t used to fasting or when it’s their first time to do fasting. This may be due to hunger pangs, intense cravings, or changes in hormonal levels,” explained Gervacio. She also says that fatigue and mood swings that may result from IF can disrupt sleep as a result of decreased food intake.

How can you tell if your sleep is being impacted? Gervacio says telltale signs include, “difficulty falling asleep due to hunger pangs and food cravings, waking up frequently during the night especially when liquid is taken close to bedtime.” 

Brown says that when an individual notices their sleep being disrupted by intermittent fasting, they might need to adjust their eating schedule accordingly. 

The answer to our question about intermittent fasting and sleep problems is a complex one, however experts do have some answers when it comes to meal timing and sleep. Gervacio recommends eating at least two to three hours before bedtime. She says that what you eat matters, too: “Focus on foods that prolong satiety like lean proteins and high-fiber foods.”

Intermittent fasting might not be for everyone — and may impact people differently based on their own needs. Check with your doctor before incorporating IF to your routine, as it might not be safe for people with certain health conditions. As always, reach out to your doctor if you experience sleep problems, whether they seem to be diet-related or not.

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