Intermittent fasting (IF) — or restricting your eating to certain hours of the day — is popular for a variety of reasons including aiding weight loss and better blood sugar and insulin control. Some say intermittent fasting can also help people age better, live longer and reduce inflammation, though the research on these benefits is far from conclusive.
Another buzzy potential “pro” of intermittent fasting: better gut health. But, like many of the proposed effects of intermittent fasting, research on the topic is scant. So, if you’re interested in a healthier microbiome and wondering if it’s worth trying intermittent fasting, here’s what experts have to say:
WHY GUT HEALTH MATTERS
“Our gut, or microbiome, is a foundational part of our overall health,” explains Elle Merrill, RDN. Though gut health may be a higher priority for people with chronic digestive conditions like IBS, Crohn’s disease and ulcerative colitis, it should be top-of-mind for anyone interested in getting or staying healthy, says Merrill. “Supporting gut health can improve your immune system response, improve digestion and absorption, decrease inflammation and stress and increase insulin sensitivity.”
HOW CIRCADIAN RHYTHM PLAYS A ROLE
One of the ways intermittent fasting seems to work is by capitalizing on our natural circadian rhythms, also known as our sleep-wake cycles.
“An excellent way to reduce stress on our body is by allowing it to follow its natural circadian rhythm, or more simply put, having a regular sleep schedule,” explains Merrill. “When this rhythm is interrupted, it negatively affects our energy and appetite levels as well as our gut health. It decreases the presence of healthy gut bacteria and increases susceptibility to inflammation and irregularity in bathroom trips.”
Interestingly, the gut also has its own circadian rhythm. “All the different types of bacteria in the gut have different responsibilities, and when disrupted, this can cause mutations or growth of dysfunctional bacteria,” says Allison Thibault, RDN.
You naturally fast while you’re asleep, which helps your gut keep its own circadian rhythm going. Some believe prolonging the fasting period, as you would with intermittent fasting, can help capitalize on those effects.
“Intermittent fasting is not required to allow your body to follow its natural circadian rhythm,” Merrill points out. But some people sleep better if they stop eating a few hours before bedtime. “While practicing IF, you may forgo a bedtime snack, giving your digestive system a break and possibly aiding sleep,” says Merril. That, in turn, could improve your gut health. “This isn’t proven for everyone, but is a common report.”
GIVING YOUR DIGESTIVE SYSTEM A “BREAK”
Another commonly cited gut health benefit of intermittent fasting is avoiding overloading your digestive system. The rationale: If you’re constantly eating, your gut doesn’t have much time to rest and digest, which can mess with optimal functioning.
There is definitely something to the idea that you don’t need to be eating all day long, nutrition pros say. “Our digestive system needs time to carry out its call to action once we’ve eaten a meal or snack,” says Merill. Taking a break between meals can also help keep blood sugar levels steady.
But, overloading your gut by eating too frequently isn’t really a thing. What is a problem, though, is regularly overeating or eating way past the point of feeling full. “When you overeat, you’re likely going to experience bloating, discomfort, fatigue and probably higher blood sugar,” says Merrill. This isn’t necessarily bad for your microbiome, but it can be uncomfortable and potentially disrupt digestion, she notes. Moreover, while your body can handle it once in a while (Think: Thanksgiving dinner), overeating frequently can cause digestive problems not to mention long-term weight gain.
WAYS TO IMPROVE GUT HEALTH
Intermittent fasting may help, but it’s not guaranteed. “You definitely do not have to incorporate IF into your life to improve your gut health,” says Merrill. Instead, experts recommend focusing on:
Getting enough fiber. This is one of the most proven and impactful ways to elevate your gut health, Merrill explains. “Slowly working toward the daily goal of 25 grams/day for women and 38 grams/day for men is important. Focus on foods like fruits, veggies, beans, nuts, avocados, whole grains and chia or flaxseeds to amp up the fiber content in your diet.”
Improving diet quality overall. “Make sure you’re consuming a well-balanced diet,” Thibault advises. In particular, eating a varied diet is important for gut health. For example, fermented foods such as kimchi and sauerkraut are rich in probiotics, which feed good gut bacteria. “Make sure you consume plenty of vegetables and fiber sources, lean proteins and healthy fats,” says Thibault.
Take the long view. “If you prefer to only eat your meals and snacks within a certain time frame daily, that’s fine,” Merrill says. “However you choose to approach a healthy lifestyle, make sure it’s sustainable and something that makes sense long-term.”
THE BOTTOM LINE
At the moment, there’s not enough research to say intermittent fasting definitely improves gut health. However, there has been some early promising research. “In studies of mice that fasted 16 hours a day, some results indicate an improved presence of gut microbiota,” says Merrill. “However, the effects did not last after the study ended.”
Ultimately, the research on this topic is still evolving. “We could definitely see more research in the future that shows improved healthy bacteria in the human microbiome while following an IF pattern,” Merrill says. “However, I don’t know if IF is necessarily worth it for gut health alone since it’s certainly possible to improve gut health without following time restrictions for eating.”
That said, Merrill notes that, in her experience, people who practice intermittent fasting end up adopting other healthy habits, too. They may attribute the benefits of these habits to fasting, even though they might have been able to make such changes (like improving hydration levels) without IF. At the end of the day, whatever eating pattern helps you improve your health is worth sticking with.