Should You Try Intermittent Fasting for Better Gut Health?

If you keep up with the latest health and wellness news, then you’ve probably heard a lot about the health craze called intermittent fasting. Studies show that this dietary practice burns fat, boosts metabolism, and lowers inflammation and blood sugar levels. Chiseled celebrities such as Hugh Jackman and Halle Berry have jumped onto this trend’s fat-busting and metabolism-enhancing bandwagon, leaving the rest of us to wonder: does the technique actually work, and if so, how do we get on board?


An ancient way of eating

Despite all the recent hype, intermittent fasting isn’t revolutionary—it’s evolutionary. Most animals eat during confined periods and then fast during short periods that often coincide with sleep. For much of our roughly 200,000-year history, Homo sapiens were no different. We ate when food was available, and fasted when it wasn’t.

Intermittent fasting, which involves cycling between fixed periods of eating and not eating, brings this evolutionary perspective back into our daily routines. There are multiple ways to practice intermittent fasting, but one of the most popular methods is constraining one’s period of eating for 8 hours followed by a 16-hour fast, the so-called “16:8 Diet”. For example, to prepare for his roles in the X-Men and Wolverine films, Jackman stuck to a regimen of only eating between the hours of 10 a.m. and 6 p.m, fasting the rest of the day and night.

Although Jackman’s strict eight-hour-long periods of eating are a common way to practice intermittent fasting, no two fasts are the same. Halle Berry simply skips breakfast, while other people eat less than 500 calories a couple days per week or commit to fasting on alternating days.

The relative abundance of food in the developed world today has thrown off our natural pattern of eating when food is available, and not eating when it is scarce. Committing to intermittent fasting sounds pretty easy until we stop to consider all of the times most of us consume calories outside of a normal pattern—the late-night dinners with friends, midnight snacks and after-work drinks.

These erratic eating habits have led to weighty metabolic disadvantages. Unlike our ancestors, modern humans build fat faster than we can burn it, a problem that has contributed to an obesity pandemic. All of this raises the question: can intermittent fasting turn back the clock to simpler, slimmer times? And how does the gut microbiome respond to fasting?


Seeing things in brown and white

For over 70 years, researchers have known that intermittent fasting has extraordinary health benefits, many of which go beyond mere weight loss. In 1946, two physiologists from the University of Chicago published a paper showing that rats that fasted every other day considerably increased their lifespan.

Although these mid-century physiologists could see the benefits of intermittent fasting, they weren’t exactly sure how it worked. Today’s scientists are finally starting to piece together the full picture.

To understand their findings, we need to understand that there are two types of body fat: brown and white. One fat (white) stores energy, while the other (brown) burns it.

White fat is what most people think of when they think of “fat.” A white fat cell contains a single, oily droplet; if you consume more calories than you burn, these droplets will collect in various places on your body such as your hips, belly and thighs. An excess of white fat around the gut area usually indicates the presence of visceral fat, a type of body fat that’s stored within the abdominal cavity, which many doctors think increases one’s chance of heart disease, type 2 diabetes, and even certain types of cancer.

Brown fat, on the other hand, is the yin to white fat’s yang. Composed of many small lipid droplets, brown fat cells also contain a high density of mitochondria which are organelles that convert the cell’s lipids into heat. The purpose of brown fat is to burn calories and generate heat.

It was once believed that only infants had brown fat, and that it disappeared completely by adulthood. However, in the late 2000s researchers discovered brown fat in the necks, guts and white fat reserves of adults. Because brown fat burns calories more easily than white fat, scientists hypothesized that if they could figure out how to give people more brown fat it would be easier for them to lose weight.

Researchers quickly discovered that exposure to low temperatures stimulates the “browning” of white fat, yielding “beige” fat cells that also burn calories faster (though not quite as fast as brown fat). However, making people feel cold all the time is both uncomfortable and impractical as a method of weight loss.


A little fasting goes a long way

Enter intermittent fasting, which also beiges brown fat cells—with the help of our gut microbiota. A 2017 study found that mice placed on a regime of every-other-day fasting both produced more beige fat and underwent significant shifts in their gut microbiota. Compared to a control group, the fasting mice had more of the bacteria Firmicutes in their guts, which stimulated increased production of the fatty acids acetate and lactate. The authors of the study suggest that these two substances could be key to the mechanism that causes the beige-ing of fat in fasting mice.

While the jury is still out on the exact details of how this happens, what is clear is that the microbiome does play a role. When the microbiota of the fasting mice were transplanted into other mice, those mice developed more beige fat cells, too.

These changes in the microbiome can have benefits beyond simple weight loss. Intermittent fasting has been explored as a treatment for diabetes-associated retinopathy (retinal damage) and is also under clinical investigation for the management of multiple sclerosis. These findings suggest that fasting not only causes microbial changes necessary for the beige-ing of white fat cells to occur, but actually changes our entire microbiome for the better.


Is intermittent fasting for you?

Despite the research pointing to the health benefits of intermittent fasting, it’s important to note that like all good things, the diet must be practiced in moderation. Jackman didn’t get his Wolverine body from diet alone—he worked with nutritionists and trainers to figure out the best balance of food and exercise.

Similarly, anyone considering venturing into intermittent fasting should first speak with a doctor to figure out an appropriate nutrition plan and exercise regimen. Some people, particularly individuals who have struggled with disordered eating, body image issues, or anxiety may want to steer clear of fasting entirely.

Of course, each person’s body is different, and there is no one weight-loss technique or health practice that is going to work for everyone. However, at least some people who hop on the intermittent fasting bandwagon see great results for their health, digestion, and for their weight as well. After getting the green light from health professionals and deciding the practice is right for you, you may reap the benefits our ancestors also sowed through fasting: a healthier and more energized body.