- Intermittent fasting, a style of eating that restricts calorie intake to certain hours of the day, or certain days of the week, has been lauded for promising health benefits, according to some research.
- However, in the midst of the coronavirus pandemic, experts don't recommend starting a fasting protocol.
- If you already do a fasting routine, experts recommend avoiding long fasts or other extreme calorie restriction.
- In the short-term, fasting can raise cortisol levels, disrupt sleep, and cause irritability.
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Intermittent fasting, a style of eating that limits food intake to specific times, has become increasing popular in recent years, and there's promising evidence for potential health benefits.
But as the novel coronavirus continues to spread and people self-isolate in their homes and stockpile groceries, now is not the time to try fasting, since it may also inadvertently weaken your immune system and leave you feeling worse, according to Alissa Rumsey, MS, RD, owner of Alissa Rumsey Nutrition and Wellness.
Even advocates of fasting have cautioned against more extreme versions of the practice right now — the intermittent fasting app Zero recently sent out an email guide from Dr. Peter Attia advising against multi-day fasting for the same reasons Rumsey mentioned.
If you do fast, keeping to your routine of milder forms of fasting, such as eating during a 10-hour window each day, isn't likely to be an issue, Attia said.
Fasting can stress your body, especially if you fast for a full day or longer
If you're used to eating regular meals and snacks, breaking your routine and forgoing food could cause a rise in your body's cortisol levels, according to Rumsey. Cortisol is a hormone often associated with stress but also linked to metabolism, blood sugar, inflammation, and even memory. Too much of it can trigger fat storage and muscle breakdown, Rumsey said.
"At a time like this, when we are already stressed, the last thing we want to do is put more stress on our bodies," she said.
Potential side effects can include lower cognitive performance, sleep disruption, and decreased mental alertness, as well as erratic blood sugar levels.
"Fasting for extended periods of time can lead to very low blood sugar followed by a large spike when you finally do eat," Rumsey said.
Attia also cautioned against fasting for two or more days based on research that it can spike cortisol levels and potentially limit immune system function.
Fasting can also be mentally taxing, especially for people at risk of disordered eating or unhealthy coping mechanisms
Fasting can also take a mental toll, particularly during a time when anxiety is already heightened. It cause people to fixate on food, sapping resources for other cognitive or emotional tasks such as working or managing stress in other ways.
It's especially risky for people with a history of disordered eating, since a rigorous food schedule might fuel an urge to restrict food or anxiety about eating.
"Only eating during a specific time frame each day disconnects us from our bodies," Rumsey said. "This can lead to an unhealthy obsession with food because all you can think about is when your next meal is going to be. It creates an "all or nothing" mentality which can lead to overeating and feelings of guilt."
There's not enough research to show fasting can "boost" the immune system in the short term
There's promising evidence for some potential long-term benefits of fasting, such as staving off symptoms of aging and possibly preventing chronic illnesses like diabetes and cancer.
However, "boosting" your immune system in the short-term isn't among those benefits.
Attia noted that it's unclear how dietary habits might help your odds of fighting off a COVID-19 infection.
"It's safe to say we don't actually know, and to suggest otherwise is probably a bit irresponsible," Attia said in a video posted on the Zero blog.
Some proponents of fasting have claimed that their protocols can help strengthen the immune system or prevent illness. One chiropractor, for instance, claimed that fasting can "clean up microbes, bacteria, viruses, parasites from your body." But there's no evidence fasting can cure or prevent the novel coronavirus.
"Unfortunately, we are seeing a lot of people playing to these fears by touting fasting and other diet protocols as a way to boost immunity, when in reality this isn't something we have much control over," Rumsey said.
However, there are helpful actions people can take to protect themselves (and their communities) beyond limiting meals. Experts agree that that social distancing and hand-washing are among the most important ways to "flatten the curve" or stop the spread of the virus.
"The best thing we can do for our immunity is to get adequate sleep and cultivate multiple coping skills to deal with stress," Rumsey said.
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