Exactly How To Use Intermittent Fasting To Lose Weight & Heal Your Gut

Vincent Pedre, M.D., is part of the mbg Collective, a curated group of our most trusted wellness advisers. Since 2009, we’ve had the brightest, most passionate mission-driven leaders in wellness share their intimate stories and world-class advice. Now we’re giving you unparalleled access to the people who, alongside mbg, are putting the “WE” back in wellness. Consider them your personal guides, there to support you and sustain you on your journey.

In my practice, I’ve repeatedly seen how intermittent fasting (IF) can help patients lose weight, feel better, and reduce their disease risk. When they stay committed to fasting long-term, sticking diligently with a plan that works for them, they get amazing results and, more importantly, sustain those results over time.

IF, which involves intermittently eating and then not eating for certain periods of time, can improve many chronic diseases1, including type 2 diabetes, cardiovascular disease, and obesity.

While it might seem obvious why you would lose weight fasting—you’re taking in fewer overall calories, presumably—researchers propose other mechanisms are also at work, including improved blood sugar control and insulin sensitivity.

But an often-overlooked benefit of IF and weight loss is gut health. Researchers find beyond its benefits on your body and brain, IF could favorably influence the balance of beneficial gut flora that protect against metabolic syndrome2, a traffic jam of issues that include high blood sugar and abdominal obesity. As a medical doctor who specializes in gut health, I've seen that studies3 show what I’ve found repeatedly in my own practice: Losing weight reduces inflammation and can improve your gut ecology.

You win on every level: You look and feel better. Gut health improves. And lower inflammation scores reduce your risk for nearly every disease.

I find many patients eat gut-unhealthy foods before bedtime. Fasting makes a great way to eliminate that bad habit. In other words, you eat a gut-friendly dinner then close up the kitchen for the night.

You’ll lose weight and have a happier gut: Studies4 show reducing or eliminating nighttime eating and prolonging nightly fasting intervals can improve various health parameters, including your gut microbiome.

Among its benefits, fasting gives your overworked gut a break from energy-intensive tasks like digesting and assimilating food. It reduces postprandial endotoxemia, which has been found to increase the risk for obesity and insulin resistance. And potentially, it improves the composition of your friendly gut flora.

Studies3 show that restoring gut balance can help you lose weight and become healthier. In one such study, researchers put overweight people on a weeklong fasting program followed by a six-week intervention with a probiotic supplement. At the end of the study, they found increased abundance and diversity of gut microbiota with these participants, including a relatively newly discovered bacteria in the genus Akkermansia, which is associated with a healthy gut and normal weight.

This study highlights how powerful even short-term fasting can be for gut health but also the importance of getting sufficient healthy gut bacteria through fermented foods or (as participants here received) a probiotic supplement. I like to think of regular, consistent fasting as hitting the reset button on your gut and overall health.

"We say that fasting is very similar to rebooting the hard drive in a computer. Sometimes, the computer gets corrupted, and you do not know exactly where the problem is. But if you just turn it off and reboot it, a lot of times, that corruption gets cleared out," says Dr. Alan Goldhamer, the lead researcher on a study on the subject5. "The same thing happens in the human body. We develop issues, and when you turn the system down with fasting and allow it to reboot, a lot of things—from gut flora and microbiota in the gut to chronic inflammatory conditions—tend to sort themselves out."

Fasting can also eliminate food sensitivities, the delayed reaction many people have to particular foods. "I initially became interested in fasting for its applications in healing the gut," says Dr. Michael Ruscio in The Complete Guide to Fasting by Dr. Jason Fung. "Many of the patients I work with have severe food sensitivities even though they have very healthy diets. For these patients there is usually some underlying inflammatory or infectious issue. Fasting can provide instantaneous relief of symptoms and aids in supporting recovery from the underlying issue."

To optimize fasting and get all these benefits, you must incorporate a healthy-gut diet. In fact, studies3 find that the more diverse your diet, the more diverse your microbiome will become and the more adaptable it will be. However, interestingly, even short-term fasting as in the above-mentioned study can improve the diversity of the gut flora.

Unfortunately, researchers believe6 we’ve lost that diversity during the past 50 years. Increasingly limited food diversity, GMOs, pesticides, and the overuse of antibiotics continue to be direct threats to the diversity of the human gut microbiome. The next generation may be the first starting with a markedly diminished variety in gut flora.

And speaking of a diverse diet, I don’t mean choosing a different type of burger during happy hour. I mean a varied plant-based diet rich in whole foods, including plenty of healthy fats and some protein, to help stimulate the type of bacterial diversity that promotes weight loss. On the other hand, a diet lacking this variety and full of processed foods will promote a less diverse, harmful gut microbiome population, which leads to weight gain.

If you’re new to fasting, I recommend eating an early dinner, stop eating for the evening, and push breakfast forward the next morning. Just by doing that even a few times a week, you can create a near-effortless 12- to 14-hour fasting window that helps heal your gut and so much more.

Even when you’re doing everything correctly diet-wise, things like chronic stress, bad sleep, and lack of exercise can all affect your gut microbiome. In two recent studies (one rodent and the other human), when researchers isolated and stabilized other factors that might alter the intestinal microbiota, they found exercise alone could positively affect your gut microbes.