Healthy Gut, Healthy Weight?

Can you leverage the microbes in your digestive tract to help with weight management? 

 You’re unlikely to hear much fanfare when you reach for the carrot sticks instead of the cookies, nor wild applause when you lace up your shoes for an evening walk instead of collapsing onto the couch. All the small decisions you make to manage your weight and your health can feel downright anticlimactic.

But you do have a cheering section for these actions—albeit an invisible one. Every healthy lifestyle choice, no matter how modest, gets noticed and celebrated by a crowd that’s trillions strong: the diverse community of microorganisms that call your gut home.

New research shows that while the microbes in your digestive tract may not directly cause you to gain or lose weight, they are thought to influence your metabolism and serve as mediators between your lifestyle choices and your body weight.

The ecosystem within

Communities of tiny living organisms exist in different habitats of the human body. “Microbiota” is the name given to the micro-organisms themselves—primarily bacteria, but also fungi (including yeasts), archaea (a recently discovered domain of single-celled organisms)[1], and viruses—while the entire environment in which they thrive is called the microbiome. The most complex microbial ecosystem on the human body is found in the digestive tract, especially within the colon.

Scientists have discovered the gut microbial ecosystem is shaped in part by our lifestyle choices, bearing the traces of everything from diet and medications to whether or not you live with pets.

And just as no two thriving forests have an identical population of organisms, no two healthy gut microbial communities are exactly alike. A greater diversity of microbes, however, is associated with better health.

Healthy metabolism takes guts

Many factors contribute to our metabolism and body weight, and in recent years, scientists have tried to find out whether our personal gut microbiome is a contributing factor.

As a starting point, they compared the gut microbes in lean people to those with a body mass index above 30—the threshold of obesity. Taken together, these studies revealed no consistent gut microbiota differences between these two groups.

Intriguingly, the weight of some animals can be altered by changing their gut microbes: In some older studies, groups of mice consuming the same diet gained different amounts of weight, depending on their gut microbiota.

In one study, researchers collected gut microbes from human identical twins (one obese, one lean); the mice receiving the microbiota of an obese twin increased their body weight more than the mice receiving that of a lean twin, even though all mice consumed the same number of calories.

Some scientists have cut right to the chase in humans, testing whether it’s possible to slim down by “resetting” the gut microbial community through fecal microbiota transplantation (transferring a gut microbiota sample from one person’s colon to another’s). Receiving a lean person’s microbes does not appear to reduce weight in a recipient with obesity, however.

Beyond body weight, gut microbes are definitely involved in other aspects of metabolic health. Manipulating the gut microbiota through diet or probiotics, for example, may improve blood glucose control in type 2 diabetes.

Gut microbes may also influence food intake by modulating appetite: a chain of events set off by our gut bacteria produces hormones that help us feel full. This means gut microbes could have an indirect influence on our body mass index.

Although it’s important to remember that gut microbes function as a complex ecosystem, scientists have managed to single out a few gut bugs that may be particularly important for maintaining a leaner physique.

Akkermansia muciniphila 

These bacteria thrive in the mucus layer that lines the interior of the gut. Multiple studies have associated them with metabolic benefits and prevention of obesity, and they appear to work by strengthening the gut barrier.

Christensenella minuta

These bacteria, which are linked with a lower body mass index in humans and seem to prevent weight gain, come “for free” if you have a particular genetic makeup. Thus, these bugs may be one way in which genes manage to contribute to weight.

Shaping your gut microbiota for weight management

Even if gut microbes don’t directly dictate the number on the bathroom scale, we may be able to leverage them to help us achieve or maintain a healthy weight. New lines of research show they’re a key element that enables us to benefit from our healthy lifestyle choices. Here’s how to get your gut microbiome to support you and your weight management goals.

Mind your diet 

Counting calories is a classic strategy for weight management—but the different macronutrients supplying those calories definitely matter to your gut microbes. Through diet, we may shape our gut microbes in a way that facilitates a healthy weight: Fiber (think vegetables, fruits, and whole grains) is crucial.

Akkermansia, in particular, are boosted through fructo-oligosaccharides, a type of prebiotic found naturally in banana, onion, artichoke, asparagus, and other plant foods, or through polyphenols such as grape and cranberry extract.

A diversity of plant foods—30 or more types per week—promotes a diverse, well-functioning community of gut microbes, while large amounts of red meat and processed foods (especially those containing emulsifiers and artificial sweeteners) are believed to have a harmful effect on the gut microbiota and may even sabotage weight-loss goals.

Maintain cardiorespiratory fitness 

Exercise is a well-known way to keep weight in check, and recent evidence suggests that higher cardiorespiratory fitness in humans goes hand in hand with gut microbiota diversity and health-promoting gut microbiota functions.

Aim to keep stress to a minimum 

Healthy eating is notoriously difficult when an individual is experiencing stress; moreover, the body’s stress response induces intestinal permeability (meaning more substances—some of them harmful—are able to pass through the gut lining and into the bloodstream)[2]. Research on the microbiota-gut-brain axis has shown gut microbiota changes in association with different stressors. It pays off, weight-wise, to manage stress and mental health as much as possible.

Avoid sleep disruptions 

It’s well established that people who experience sleep disruptions, including sleep apnea and the “jet lag” induced by night shifts or staying out too late, have a harder time maintaining a healthy weight.

The changes in gut microbiota composition caused by sleep disturbances could be responsible for the metabolic problems that occur, showing the critical importance of getting enough shut-eye to help your bugs take care of you.

Our gut microbes not only bear the traces of our lifestyle choices, but they may also be an essential part of how these choices lead to a healthy weight. The exciting new area of science linking gut microbes with health could, over time, yield ways to manipulate microbial ecosystems for targeted health effects, offering each of us personalized strategies for weight management based on our unique collection of gut microbes.

Your gut microbes on a crash diet

Drastically restricting certain foods on a temporary basis—otherwise known as “crash dieting”—is a typical strategy for weight loss. But such extreme short-term strategies could end up backfiring.

One study found overweight mice that had successfully slimmed down through dieting developed a persistent gut microbiota pattern that actually contributed to faster weight regain once they resumed a normal diet. Plus, the extent of the animals’ weight regain after the crash diet was predictable, based on how their gut microbiota looked.

Basically, you’re probably better off forgoing drastic dietary changes and sticking to lifestyle changes you can maintain in the long run.

Supplements for better gut health

Remember that more is not always better in the finely tuned gut environment, so check with a health-care practitioner about the dose that’s right for you.